Viktor Frankl was a fascist and a nazi collaborator. He was a member of the Fatherland Front from 1934, the far-right austrofascist party.

Just to be clear here, the Austrofascists were not Nazis, and weren't friendly with the Nazis. They were anti-democratic, Christian fascists, yes, but they were at the same time seen by many as the only real alternative to, well, Austria joining Nazi Germany. The Frankl biography by Timothy Pytell has this to say:

Since the civil war in 1934 led to Austrofascism, and the Socialist Party was outlawed, the political options for Viennese Jews became extremely limited. The most obvious alignment for Jews was to support the authoritarian, Christian government. The choice was clear, because the most likely successor to the Austrian corporate state was not social democracy, but National Socialism. Thus, “Jews of nearly all political shades” dissociated from the Socialists and declared “their loyalty to the new Austrian state and the Fatherland Front. One might term such behavior opportunistic … but it was merely pragmatic.”

Frankl’s political allegiances are not explicit. We know he became a member of the Fatherland Front on 23 February 1934, and was described as “politically perfect” on 8 February 1937 in a survey of Fatherland Front party membership. However, it is likely that Frankl’s membership in the Front was mandated by his position at the state hospital Am Steinhof. Signifi cantly, the Front’s membership survey is the only document in his Gauachten fi le (these fi les were created by the Nazi party and described individuals’ ideological orientation) in the State Archive in Vienna.6 It also appears the full documentation is missing because many fi les were cleansed after the war.

You can learn two things from Pytell: First, there may have been pragmatic, opportunistic reasons for Frankl to join the Austrofascists, even for him as a former social democrat. Additionally, there may have been professional reasons for this. Second, the Gauachten references an earlier document from 1937 describing him as politically perfect. So this reference was not one by the Nazis about Frankl's allegiance to Nazism, but one by the Austrofascists about Frankl's allegiance to Austrofascism.

This is to say: Your interlocutor seems to have some stuff mixed up, although some pop history sources has the story essentially like they told you, so it doesn't seem like it's their error.

I do not know anything about Frankl's time after Austrofascism though.

Edit: An article in a jewish magazine that makes similar claims to your interlocutor can be found here, and a debate that challenges some of it here

Victor Frankl was imprisoned in Theresienstadt between 1942 and 1944. Theresienstadt was a sort of hybrid between concentration camp, transit camp, and ghetto established in a garrison city in Bohemia. Many of its prisoners were elderly German and Austrian Jews. Having an "elders ghetto" supported the Nazi regime's ruse that the Jews being deported to Eastern Europe were actually going to work at some new settlement, not being murdered, since it would have seemed unlikely for older people to be performing manual labor. Another group of Austrian and German Jews sent to Theresienstadt were disabled or decorated war veterans or people who were culturally or professionally prominent -- the reason for this being that their disappearance might provoke unwanted attention and maybe even international condemnation. Prisoners at Theresienstadt faced starvation, disease, forced labor, overcrowded and unsanitary conditions, and ultimately, deportation and murder at Auschwitz and elsewhere. Theresienstadt was absolutely not a "low-security ghetto for upper-class Jews," and the commenter here is reproducing Nazi propaganda that characterized it as a spa town the regime generously granted Jewish retirees.

According to Timothy Pytell's article (which the commenter mentions, it's called "The Missing Pieces of the Puzzle: A Reflection on the Odd Career of Viktor Frankl", published in 2000), Frankl worked as a psychiatrist in Theresienstadt and helped new arrivals acclimate to ghetto life. He also established what Pytell called a "suicide intelligence network," intended to identify and intervene with people suspected of being suicidal. Preventing suicide seemed to be one of Frankl's highest goals, so this makes sense. However, suicide in Theresienstadt was strictly forbidden, it also served the Nazis' purpose of keeping prisoners alive under unbearable conditions so their labor could be exploited. Since Frankl was a doctor and appears to have been involved in the administration of the public health department at Theresienstadt, he may have had access to certain benefits that prisoners lower than he in the internal hierarchy wouldn't have had. He would have also been faced with morally fraught choices. Again, I think it's grotesque to say that this would make Frankl a Nazi collaborator.

Pytell writes that Frankl leaves his readers with the impression that he was in Auschwitz for a significant time, while he barely mentions Theresienstadt at all. Apparently, he was in Auschwitz for only a few days before being transferred to a subcamp of Dachau. I've never read Frankl's books, so I don't know if this is a fair reading of his work, and if so, I don't know why he might have made this choice. Maybe he (or his editors) were using "Auschwitz" as a synecdoche for all his experiences during the Holocaust, assuming that the public would be more familiar with that name than they would be with Theresienstadt. Pytell criticizes Frankl for implying that he could "capture the reality of experience in Auschwitz" without having been faced with "the worst of the horrors of the camps." Having not actually read Frankl, I can't comment on this -- maybe he did misrepresent himself in a way that makes his work less credible -- but I would not say that Frankl is less of a Holocaust survivor because he was in Dachau and Theresienstadt for longer than he was in Auschwitz.