Anyone with a decent level of education who engages in such denial has a personal issue or predjudice obscuring their judgement-- internalized racism, bias against Jews, or a similar mental obstacle. The exhaustive documentation, the physical evidence, the eyewitness testimony... There's no obstacle to believe, except having the moral turpitude to admit that humanity does such things to itself; some people will never have that capacity.

There is simply no reasoning with such people, as reason cannot dissolve their own internal mental restraints.

u/GrandfatherRat is correct that there is no true conversation to be had with a denier. However, there can be conversations with someone who has seen denialist literature or propaganda and is wondering about its validity.

The key in such a case is to remember that denialists speak in half truths. Think of unspoken parenthetical statements.

Hence "Most deaths in German camps came in the last 90 days of war from Typhus and starvation due to Allied saturation bombing" becomes "Most deaths in German (concentration/work) camps (liberated by the allies rather than evacuated by the Germans) came in the last 90 days of war from Typhus (due to horrid, unlivable conditions in the camps) and starvation due to Allied saturation bombing (which nevertheless did not lead to similar rates of starvation in German, non-camp citizenry because non-camp citizens were not already on starvation rations)."

In other words, you simply have to point out that they use only a few, very specific examples to "prove" their points. Their is a reason that the same 6 examples of "proof" show up in all their literature and are almost given verbatim. These are carefully crafted to leave out the important details. Another example is "lamp shades of human skin, soap of human fat, photos of stacked bodies were all propaganda hoaxes" becomes "lamp shades of human skin, soap of human fat, and photos of stacked bodies (oops, maybe they were mistaken on this one) were all propaganda hoaxes (read repeated rumors which were not accepted by Holocaust historians).

Remember that the best thing you can do is have a work by a Holocaust historian to which you can refer the curious soul. Read the work yourself so that you can understand the scope and nature of the Holocaust. Then you will be able to recognize the half-truths of the deniers.

r/AskHistorians mods use this copypasta:

I hope you can appreciate that it can be a fraught subject to deal with. While we want people to get the answers they are looking for, we also remain very conscious that threads of this nature can attract the very wrong kind of response. As such, this message is not intended to provide you with all of the answers, but simply to address some of the basic facts, as well as Holocaust Denial, and provide a short list of introductory reading. There is always more than can be said, but we hope this is a good starting point for you.

##What Was the Holocaust?

The Holocaust refers the genocidal deaths of 5-6 million European Jews carried out systematically by Nazi Germany as part of targeted policies of persecution and extermination during World War II. Some historians will also include the deaths of the Roma, Communists, Mentally Disabled, and other groups targeted by Nazi policies, which brings the total number of deaths to ~11 million. Debates about whether or not the Holocaust includes these deaths or not is a matter of definitions, but in no way a reflection on dispute that they occurred.

##But This Guy Says Otherwise!

Unfortunately, there is a small, but at times vocal, minority of persons who fall into the category of Holocaust Denial, attempting to minimize the deaths by orders of magnitude, impugn well proven facts, or even claim that the Holocaust is entirely a fabrication and never happened. Although they often self-style themselves as "Revisionists", they are not correctly described by the title. While revisionism is not inherently a dirty word, actual revision, to quote Michael Shermer, "entails refinement of detailed knowledge about events, rarely complete denial of the events themselves, and certainly not denial of the cumulation of events known as the Holocaust."

It is absolutely true that were you to read a book written in 1950 or so, you would find information which any decent scholar today might reject, and that is the result of good revisionism. But these changes, which even can be quite large, such as the reassessment of deaths at Auschwitz from ~4 million to ~1 million, are done within the bounds of respected, academic study, and reflect decades of work that builds upon the work of previous scholars, and certainly does not willfully disregard documented evidence and recollections. There are still plenty of questions within Holocaust Studies that are debated by scholars, and there may still be more out there for us to discover, and revise, but when it comes to the basic facts, there is simply no valid argument against them.

##So What Are the Basics?

Beginning with their rise to power in the 1930s, the Nazi Party, headed by Adolf Hitler, implemented a series of anti-Jewish policies within Germany, marginalizing Jews within society more and more, stripping them of their wealth, livelihoods, and their dignity. With the invasion of Poland in 1939, the number of Jews under Nazi control reached into the millions, and this number would again increase with the invasion of the Soviet Union in 1941. Shortly after the invasion of Poland, the Germans started to confine the Jewish population into squalid ghettos. After several plans on how to rid Europe of the Jews that all proved unfeasible, by the time of the invasion of the Soviet Union in 1941, ideological (Antisemitism) and pragmatic (Resources) considerations lead to mass-killings becoming the only viable option in the minds of the Nazi leadership. First only practiced in the USSR, it was influential groups such as the SS and the administration of the General Government that pushed to expand the killing operations to all of Europe and sometime at the end of 1941 met with Hitler’s approval.

The early killings were carried out foremost by the Einsatzgruppen, paramilitary groups organized under the aegis of the SS and tasked with carrying out the mass killings of Jews, Communists, and other 'undesirable elements' in the wake of the German military's advance. In what is often termed the 'Holocaust by Bullet', the Einsatzgruppen, with the assistance of the Wehrmacht, the SD, the Security Police, as well as local collaborators, would kill roughly two million persons, over half of them Jews. Most killings were carried out with mass shootings, but other methods such as gas vans - intended to spare the killers the trauma of shooting so many persons day after day - were utilized too.

By early 1942, the "Final Solution" to the so-called "Jewish Question" was essentially finalized at the Wannsee Conference under the direction of Reinhard Heydrich, where the plan to eliminate the Jewish population of Europe using a series of extermination camps set up in occupied Poland was presented and met with approval.

Construction of extermination camps had already begun the previous fall, and mass extermination, mostly as part of 'Operation Reinhard', had began operation by spring of 1942. Roughly 2 million persons, nearly all Jewish men, women, and children, were immediately gassed upon arrival at Bełżec, Sobibór, and Treblinka over the next two years, when these "Reinhard" camps were closed and razed. More victims would meet their fate in additional extermination camps such as Chełmno, but most infamously at Auschwitz-Birkenau, where slightly over 1 million persons, mostly Jews, died. Under the plan set forth at Wannsee, exterminations were hardly limited to the Jews of Poland, but rather Jews from all over Europe were rounded up and sent east by rail like cattle to the slaughter. Although the victims of the Reinhard Camps were originally buried, they would later be exhumed and cremated, and cremation of the victims was normal procedure at later camps such as Auschwitz.

##The Camps

There were two main types of camps run by Nazi Germany, which is sometimes a source of confusion. Concentration Camps were well known means of extrajudicial control implemented by the Nazis shortly after taking power, beginning with the construction of Dachau in 1933. Political opponents of all type, not just Jews, could find themselves imprisoned in these camps during the pre-war years, and while conditions were often brutal and squalid, and numerous deaths did occur from mistreatment, they were not usually a death sentence and the population fluctuated greatly. Although Concentration Camps were later made part of the 'Final Solution', their purpose was not as immediate extermination centers. Some were 'way stations', and others were work camps, where Germany intended to eke out every last bit of productivity from them through what was known as "extermination through labor". Jews and other undesirable elements, if deemed healthy enough to work, could find themselves spared for a time and "allowed" to toil away like slaves until their usefulness was at an end.

Although some Concentration Camps, such as Mauthausen, did include small gas chambers, mass gassing was not the primary purpose of the camp. Many camps, becoming extremely overcrowded, nevertheless resulted in the deaths of tens of thousands of inhabitants due to the outbreak of diseases such as typhus, or starvation, all of which the camp administrations did little to prevent. Bergen-Belsen, which was not a work camp but rather served as something of a way station for prisoners of the camp systems being moved about, is perhaps one of the most infamous of camps on this count, saw some 50,000 deaths caused by the conditions. Often located in the Reich, camps liberated by the Western forces were exclusively Concentration Camps, and many survivor testimonies come from these camps.

The Concentration Camps are contrasted with the Extermination Camps, which were purpose built for mass killing, with large gas chambers and later on, crematoria, but little or no facilities for inmates. Often they were disguised with false facades to lull the new arrivals into a false sense of security, even though rumors were of course rife for the fate that awaited the deportees. Almost all arrivals were killed upon arrival at these camps, and in many cases the number of survivors numbered in the single digits, such as at Bełżec, where only seven Jews, forced to assist in operation of the camp, were alive after the war.

Several camps, however, were 'Hybrids' of both types, the most famous being Auschwitz, which was a vast complex of subcamps. The infamous 'selection' of prisoners, conducted by SS doctors upon arrival, meant life or death, with those deemed unsuited for labor immediately gassed and the more healthy and robust given at least temporary reprieve. The death count at Auschwitz numbered around 1 million, but it is also the source of many survivor testimonies.

##How Do We Know?

Running through the evidence piece by piece would take more space than we have here, but suffice to say, there is a lot of evidence, and not just the (mountains of) survivor testimony. We have testimonies and writings from many who participated, as well German documentation of the programs. This site catalogs some of the evidence we have for mass extermination as it relates to Auschwitz. I'll close this out with a short list of excellent works that should help to introduce you to various aspects of Holocaust study.

##Further Reading

• "Third Reich Trilogy" by Richard Evans
• "Hitler, the Germans, and the Final Solution" by Ian Kershaw
• "Auschwitz: A New History" by Laurence Rees
• "Ordinary Men" by Christopher Browning
• "Denying History" by Michael Shermer and Alex Grobman
• AskHistorians FAQ

To debunk the claims is to first understand how they came up with such a ridiculous conclusion in the first place. They have probably watched "The Greatest Story Never Told," a "documentary" which is a self-described "unbiased" and "truthful" video, championing the phrase, "The truth fears no investigation."

The documentary itself is a string of cherrypicked parts of other documentaries and fringe speakers talking about the subject along with the creator's own dialogue in between.

The notion of Holocaust denial comes from poorly made facile info graphs which show gas chambers with wooden doors and the fact that there were no mass graves at Concentration camps (there might also be math which predicates that all the Jews were killed at Auschwitz and points out the fluctuating death toll in the camp between the years).

Okay, here is one thing to know about the Holocaust, a majority of the deaths were not perpetrated inside the camps and gas chambers, but through mass local executions either by collaborating forces or the Nazis themselves. If my memory serves me correctly it was around 3 million by 1941. For example, in Ukraine alone, around 850,000 Jews were killed (Along with 3 million Ukrainians as well). https://en.wikipedia.org/wiki/The_Holocaust_in_Ukraine

Secondly, they will also point the Leuchter report as undeniable proof that there is an empirical basis to Holocaust denial. This is simply a gullibility to pseudo science. I am no scientist myself and I'm sure I would butcher the actual criticisms of the report myself, so I will leave this to you. https://en.wikipedia.org/wiki/Leuchter_report#Claims_and_criticism