Yet for obvious reasons, I find it deeply troubling to allow that kind of stuff to go unanswered.
And yeah, for those of you who want to know I use the same avatar there as I do here.
There is no magic bullet here, but if you really give it the time and get to know them as individuals, it can be done.
De-escalate the conversation. Talk to them about really ordinary stuff. Maybe ask them for a little background about who they are (avoiding names and anything that could identity them offline obviously so they don't get doxxed) and how they reached their views. Maybe they read a book or saw something on YouTube.
Maybe crack a few jokes. Share a few Hitler memes or maybe some parodies of Hitler's rants from the movie Downfall. It's a good rule of thumb that if someone has no sense of humour, they are unreachable. being able to laugh at yourself means being able to admit you do things or can believe things that are absurd or counter-intuitive. That's a very solid starting point for identifying who is open and who is not.
Chances are they were not raised as holocaust deniers and went through a process of "learning" about these ideas or different conspiracy theories. When you start to see them more as people, they'll stop seeming so scary and it becomes something more profound and tragic.
I've been a communist for over a decade and the worst part of the conversation was feeling guilty and responsible for the deaths of 100 million people because I shared the same ideology as the perpetrators. You are forced to ask the question of whether you could have done these kind of things yourself (and yes, I probably could have when I was younger and didn't know what I was doing in a "wrong place, wrong time" kind of scenario). These kind of subjects are so unbelievably horrific that it is incredibly difficult to process, yet no-one on the other side gives you credit for what that actually involves a gratuitous, violent personal assault on your identity or your values. you share not simply the same ideas as some of the worst people who ever existed, but you share your humanity with them too. There is no hard line between good and evil and all we have is the choices we make. anyone and everyone could become involved in these kind of atrocities under the wrong circumstances and that is a shocking realisation.
The psychological process of accepting that level of horror, brutality, cruelty and sadism is really beyond anyone outside of a mental hospital and our popular account of history doesn't do justice to just how bad things really were. Believing the holocaust happened is not the same as understanding it or having lived through it. I watched several eyewitness accounts of the atrocities under the Khmer Rouge in cambodia ("Enemy of the People" is an extraordinarily daring documentary based on a series of interviews with perpetrators and with Noun Chea, "Brother Number 2", second only to Pol Pot ). But when you have invested so much of yourself and your worldview in the belief that the world is just, that people make rational decisions and are generally "good"- having to confront the fact that all of those foundational assumptions for our everyday interactions doesn't hold true, it's traumatic. When I learned that Communists had used gas vans against their own citizens, I basically just burst in to tears as that crossed the psychological threshold of "ok, you're no better than a Nazi now".
In the end, the difficulty of engaging with people who didn't understand my politics meant that my first girlfriend was a neo-nazi and a holocaust denier. She was involved in it for about a year. We got to know each other online and formed a bond because we were both outsiders and both highly political. We learned to laugh at each others beliefs and ourselves. But we had already both reached the tipping point where we knew it was BS even if we couldn't quite accept that. However, there was no where to go to talk about it, no kind of therapy available to unravel our identities from these beliefs, so we had to rely on each other to really come to terms with that kind of trauma. We are very good friends and she has left behind her neo-nazi days, is deeply ashamed and disgusted by her past antisemitism and has come out as bisexual and is more supportive of LGBT rights. I've come a long way, even if I was more deeply invested in communism and remain haunted by it to a point where it's never really left me (despite my best efforts). It takes an awful lot of love to forgive yourself for being involved with something like that and it remains the hardest thing I've ever had to do.
