Isn't there a limit though?
If someone says 'You know, Hitler (yeah, Godwin's law...) had a point - maybe we would be better off without the Jews...'
The notion that I should somehow go 'Hmm, that's an interesting point of view. Have you considered that maybe genocide is a bad thing and we should avoid it?. But of course, you're free to think that, and I totally respect your anti-Semitism as a legitimate point of view...'seems somehow completely wrong...
One site I know declared that promoting the Nazis (or anti-Semitism in general) was trolling.
To play devil's advocate... from a purely academic or scientific point of view, yes this kind of discussion would be fine. But in reality, humans are always the one doing the talking (at least so far), and they have emotions and, importantly, morals (though not always the same morals). A discussion around this premise is decidedly amoral to most nations of the past 65 years. But to be clear, I would almost certainly never entertain such a discussion or premise in chat here and would consider it trolling, per Stephen's comment. I would flag or use RO powers where available to handle it.
From a purely academic or scientific point of view, this "discussion" would not be fine. It's exclusionary and horribly offensive. You would be forcibly removed from any academic or scientific forum if you tried something like this. I can guarantee it because I've seen it happen. Go to a conference and try it yourself if you don't believe me.
I don't think the point is to feign acceptance. I think the point is to have a constructive debate. In a constructive debate even the worst of arguments can be used to build upon and reach an improved conclusion. You can reject an argument politely and state your reasons. Compare "I see how the media may have influenced you to feel that way, but it's a massive stereotype. I disagree with your reasons or that it would solve anything. Racial discrimination and trampling of human rights is never a solution" with "yeah you would you effin Nazi scumbucket wouldn't you, go back to your gas chambers"
The point here isn't that you have to respect anti-Semitism in chat. You can, and should, flag that sort of thing, and quickly steer the conversation away from it. What you shouldn't do is have a big debate about it in chat. Similarly, you should be wary of less obvious but still controversial topics: don't bring them up unless you're really sure everyone's okay with it and capable of reasonable discussion, and if someone brings them up despite that, be ready to steer conversation away and flag for help if necessary.
Just to muddy the waters even more, what about the multiple instances of genocide in the Old Testament? Consider how you might go about having a respectful discussion with a deeply religious Christian.
@VictorStafusa "... would sound completelly sarcastic for me." That's because being nice is found rarely and you rather want to believe in the opposite. Sarcasm and truly nice behavior is indistinguishable.
@StephenLeppik - Just to prove Shog's point to you: there's a lot of people who - with good reason - consider Socialism about as bad as Nazism (I won't bother offering arguments as that's not the point of this comment - but the point is, right or wrong, they have a valid point). If you're allowed to ban promoting Nazism based on your reasons, are those people allowed to also ban promoting Socialism based on theirs? Not so simple now, is it? You can't simply say "this is good politics, this is bad politics" precisely because there are no neat objective lines no matter how you pretend.
@DVK I don't mind not talking about politics but "right or wrong they have a valid point" is not a sensible thing to say about anything.
@DVK Nazism is about hate speech. I would disagree on them being anywhere near as equally harmful as socialism since we have a mixed capitalist/socialist society, as does most of the rest of the world.
@angorsaxon - as I said, "I won't bother offering arguments". This isn't the venue. If you want to know the reasoning behind this, Google. Or ask on Politics.SE if you can fit it into SE-answerable question.
How about "Vaccines cause autism" in an SE forum? Less instinctively problematic than Nazis, but still quite a dangerous bit of misinformation. Just going along with it causes problems for herd immunity and really does encourage diseases directorsblog.nih.gov/2016/03/22/
@DVK - Yes. Of course promoting either Communism in the form of suppressing or murdering civilians in the same way that Nazism suppressed and murdered their own civilians should be banned. And in the context of chat at SE, it is most certainly in violation of the "Be Nice" policy. Your example is rather simple, and I can simply say that when a Government enacts policy to murder its own civilians that is bad politics. Furthermore, if you can locate a Nazi politician, let the local authorities know. Banning would be getting off easy.