This is pretty much rank Holocaust denial and all of these claims fall apart under scrutiny.

"It is a remarkable coincidence that of the ~8 out of 40 concentration camps that were allegedly used to systematically exterminate, rather than provide forced labor like the Americans did with the Japanese, or the Russians with their Gulag system, every single one of them were liberated by the Soviet Union

Well, aside from the fact that American internment of Japanese was not forced labor (the only reason I can think of for including this aside from rank ignorance is to set up some sort of false equivalency thing), it is not surprising that the Soviets liberated these camps. Most of Aktion Reinhard's camps- which were camps explicitly set up to exterminate mass numbers of Jews- were located within the former state of Poland. This was where the SS had the greatest free reign over administrative policy and was proximate to a very large population of Jews. Moreover, most of the Reinhard camps were dismantled by 1943, so the Soviets technically did not "liberate" them. Some of the Polish camps continued to operate after 1943, most notably Auschwitz, but a lot of them were demolished by the retreating SS in advance of the Red Army. Denialists love to state that the gas chambers were postwar reconstructions, but this was no state secret. The Auschwitz state museum made no secret that its camp was a reconstruction.

Initially a few of the concentration camps liberated by the allies were labeled as "Death Camps" and supposedly possessed gas chambers, but it was later found that all those accounts were fabricated, and that the entirety of the casualties at those camps was caused by a rampant typhus outbreak and undernourishment, the result of the devastating allied Air bombardment that eradicated their entire agricultural system and infrastructure earlier in the war.

This is plain stupid. This answer of mine delves into the issue of the camp overcrowding and how much of the responsibility lies not with Allied aerial bombardment (see that "neat" sleight of hand there), but the callousness of camp officials and the Nazi policies that increasingly relied on slave labor with little thought as to how to feed these laborers. Fun fact, the V-2 program probably killed more people constructing the missiles than when they were used against civilian targets. The SS-run slave labor system cared little for human wastage.

All of the confessions obtained by German Officers were following intense physical and mental torture by the USSR NKVD. Not exactly conducive for belief. In fact, some of the Officers gave such outrageous and ridiculous confessions of depravity, that it was fairly obvious that they were intentionally exaggerating in protest.

There was NO torture for the IMT Nuremberg tribunals. As /u/commiespaceinvader mentions in their comment:

As can be seen from the sources the article puts forward, the allegations of torture of prisoners in order to confess in connection to Nuremberg have never been substantiated. They either cite themselves or other deniers, whose works have been thoroughly debunked. No document exists that proves the defendants at Nuremberg were tortured because they were not. By all accounts, including those of the defendants themselves in Nuremberg as well as other cases (see the writings of Hans Frank or Erich von dem Bach) they have not been tortured and have not observed torture.

As for the last two sections, it is hardly a surprise that the defendants in Nurember acted surprised about hearing of the Holocaust. I mean, they were maintaining their innocence. And yet, several former Nazis who testified against them, were not surprised. Here, one could also cite from the testimony of Erich von dem Bach who testified against his former colleagues and basically admitted at murdering and torturing on order of Ernst Kaltenbrunner and the likes.

So, in conclusion, the Nuremberg Trials have been assessed critically by non-denier historians and had their problems discussed critically. However, not in the sense this article claims. While there were aspects to them that we nowadays would see in a critical light, they were surprisingly fair and not a case of "victor's justice". The core claims of the IHR article, that there is no evidence of large scale murder, that evidence was falsified, and that confessions had come from torture are all false and can not be substantiated with the available evidence. The IHR article amounts to lies, half-truths and cherry picking and in that sense is a typical piece of denialist propaganda and lies.

Now some of the American NMT interrogations did use questionable techniques, especially for the Malmedy investigation, but this was not NKVD torture or Soviet show trial-level stuff. There is abundant evidence- linked in /u/Georgy_K_Zhukov 's response- that corroborates the charges in the trial. If anything, the postwar justice system undersold the degree of Wehrmacht complicity in atrocities and many guilty parties died in their beds uncharged.

No "Gas Chambers" in Auschwitz existed when the Soviet Armies discovered them in 1944 / 1945. The camp did have a few air raid bankers that had been destroyed by bombs during the allied bombardment of camp, so the Soviets rebuilt these and added some holes in the roof, claiming they were the gas chambers the Germans used to conduct mass killings. A couple decades ago, the curators of Auschwitz had to admit that the current gas chambers on site were the ones the Soviets rebuilt. The death toll the Soviets initially reported at the camp was around 4 or 5 million, but over time the estimate has reduced gradually by to a couple hundred thousand.

Again, this is a level of stupid that sounds impressive at first, but falls apart like a poorly-made house of cards under scrutiny. To belabor a point, the reconstructions were not a secret or embarrassment. Moreover, the exaggerated death toll was part of a postwar attempt by Poles to make Auschwitz a site of Polish martyrdom and suffering. Much of the commmemoration and memory politics of the Eastern bloc under communism scarcely mentioned the Jews or antisemitic angles of Nazi massacres. The memorial at Babi Yar for example mentioned the murder of Soviet citizens and only mentioned the Jewish origins of the massacred in the 1980s, and even then the memorial used Yiddish instead of Cyrillic.

The amount of casualties that the Soviets claimed could not mathematically be cremated in the 2-3 years the Germans allegedly conducted the extermination. It doesn't even come close, because to cremate a body it takes a process of 6-8 hours even in MODERN cremation ovens.

Trying to use modern cremation methods to extrapolate Holocaust cremation is a common denialist method and one that ignores one very simple fact. Modern crematoria are businesses predicated on respectful individual cremation. The mass cremations of the Holocaust were not designed for human dignity and would try methods that would be unthinkable for a modern funeral business. This included using large number of corpses as their own fuel. Yechiel Reichman, a Jewish inmate at Treblinka testified postwar:

The SS “expert” on bodyburning ordered us to put women, particularly fat women, on the first layer on the grill, face down. The second layer could consist of whatever was brought—men, women, or children— and so on, layer on top of layer. . . . Then the “expert” ordered us to lay dry branches under the grill and to light them. Within a few minutes the fire would take so it was difficult to approach the crematorium from as far as 50 meters away. . . . The work was extremely difficult. The stench was awful. Liquid excretions from the corpses squirted all over the prisoner-workers. The SS man operating the excavator often dumped the corpses directly onto the prisoners working nearby, wounding them seriously.

There were also patents by J.A. Topf & Söhne for recirculation of body fat into the furnaces, something that was really only practical for mass cremations. Although these mass burnings used both wood, oil fuel, and coke, only oil was in truly short supply in the Third Reich during the height of its mass disposal efforts (1942-43). The cremation pits of the Reinhard camps were located in largely wooded areas in Poland, so this fuel was readily available. The permanent crematoria were often closely connected to the SS's use of slave labor for industrial enterprises, making their supply of fuel such as coke much easier.

like what happened to Ernst Zundel in the 90's.

Zündel is no martyr. He broke the laws of his host country Canada as well as German law. German laws on Holocaust Denial may look draconian at first glance, but the threshold for prosecution is high and it does not criminalize thinking the Holocaust isn't real. It is not a thought-crime in Germany and there are legal procedures to rise to the level of prosecution, and there is an appeal process too. Zündel still publishes his tripe in countries where it is legal. His books are pretty much worthless from the vantage point of historical knowledge. Zündel and his ilk are not contributing to a historical debate. They write easily disprovable junk that only generates noise.

So /u/kieslowskifan already addressed pretty much all of this in their usual outstanding manner. To reiterate, this is rank Holocaust denial and frankly your friend is simply talking the worthless shit Holocaust deniers put out there.

Initially a few of the concentration camps liberated by the allies were labeled as "Death Camps" and supposedly possessed gas chambers, but it was later found that all those accounts were fabricated,

This has already been addressed but to further the point, these camps did not "allegedly" have gas chambers, they did indeed have them. Mauthausen, Neuengamme and Natzweiler-Stutthof all had gas chambers and were all liberated by the Western Allies. While these camps weren't used as death camps in the sense that Treblinka et. al. were, the gas chambers alsong with other methods were in use there, among other things during the so-called Kugelaktion where Soviet POWs were killed in great numbers in various camps, especially Mauthausen. This is not just confirmed through documents produced by the Nazis themselves but has also been confirmed by e.g. the Mauthausen commander Franz Ziereis.

All of the confessions obtained by German Officers were following intense physical and mental torture by the USSR NKVD. Not exactly conducive for belief. In fact, some of the Officers gave such outrageous and ridiculous confessions of depravity, that it was fairly obvious that they were intentionally exaggerating in protest.

This has also been addressed by /u/kieslowskifan below but we even have confirmations of "depravity" from people who were just witnesses at the IMT Trial. Erich von dem Bach-Zelewski, responsible for "partisan warfare" in Belarus never faced any war crimes charges, was only imprisoned a very short time and testified extensively at the IMT to, among other things, the Wehrmacht's command plan to reduce the Slavic population of Eastern Europe by 30 million.

No "Gas Chambers" in Auschwitz existed when the Soviet Armies discovered them in 1944 / 1945.

Here is a facsimile of the Auschwitz Central Construction Office's report on finishing the gas chambers and crematoria, here is a faksimile of the daily reports that states they were putting in concrete floor in the gas chambers, and here's a construction plan for the gas chambers and crematoria. Also, for good measure, here is an actual picture of bodies of Hungarian Jews being burned in Auschwitz.

The amount of casualties that the Soviets claimed could not mathematically be cremated in the 2-3 years the Germans allegedly conducted the extermination.

According to Höss himself as well as the Töpf&Söhne and Zentralbauleitung documents, the capacity of both the Red and the White House – the first two gas chamber complexes in Birkenau – already exceeded 600 prisoners a day: His own estimation of the capacity of the Red and White Houses was 800 prisoners in one gassing in the Red House and about 1200 in the White House, which when combined gave them the capacity to kill 2000 prisoners at once. That was just in one gassing however. One such process consisting of getting people into the chambers, having them exposed to the gas for 8 to 20 minutes, and then clearing out the chamber and transporting the corpses into the crematoria, if estimated generally takes about two hours (we do have examples where they went faster than this), so the daily killing capacity of the Red and White House alone, assuming 16 hour and not 24 hour operations of the camp was at that point already around 16,000 people a day.

The main problem for the Nazis however was not so much the killing capacity of the gas chambers but rather the incineration rate of the crematoria. While the gas chambers could handle killing 16.000 people a day, the crematoria couldn't handle burning that many bodies in a comparable time frame. This was among other things to be addressed by the Crematoria complexes (consisting of a crematorium and a gas chamber in one building) that were ordered to be build in mid-1942 and for which construction started in August 1942.

Starting in March 1943 with Crematorium II, later to be followed by III, IV, and V, the first big gas chamber-crematorium complex went into use in Auschwitz. Crematoria II e.g. was in continuous use for almost the rest of the history of the entire camp, being shut down on November 24, 1944 and having operated for 603 days.

In each of these the gas chamber had about 230m2 and a capacity according to the SS of about 2000 people in one gassing. Once again, the problem for the SS remained cremation. While the ovens had expanded significantly, they still could not keep up with the rate of killing. They were still able to keep up enough though: Calculations made by the Zentralbauleitung on June 28, 1943 showed the crematoria could burn 4,416 corpses per day—1,440 each in crematoria II and III, and 768 each in crematoria IV and V. This meant that the crematoria could burn over 1.6 million corpses per year.

Ernst Zündel

Again, /u/kieslowskifan already talked about this particular piece of shit but as is the usual case with these denialist dimwits, he was prosecuted in Germany not solely for the nonsense he published on the Holocaust but also for incitement to racial hatred, having made several anti-Semitic statements.

Yes, there are a number of (debunked) denialist talking points there, not to mention false equivalences such as comparing the Japanese-American internment camps to Nazi Concentration Camps. All in all though it is a number of points to address in one go, so I would direct you to the FAQ Section on Holocaust Denial as much of it is covered there, with a specific focus on the Monday Methods thread by /u/commiespaceinvader.

It is worth noting how easy it is for your friend to spout this rubbish, how much mileage he attempts to make from the absence of information and to imply sources are deceitful. He offers no research, just a lot of cynicism.

To rebuke this crap on the other hand takes care, marshalling of facts, citing specifics. Much harder, more time-consuming, and ultimately exhausting.

Denial is really easy to churn out, like knocking down a building is easier then constructing it. Those who do so, usually without any good faith (they refuse to engage with any reasoned rebuke), will sook at their 'right to be heard' being questioned... but this thread shows how damaging assertive ignorance and calculated misinformation is to reason and civilisation.