Do you have a specific definition of "nazi" in mind we can apply in a reasonable way?
The usual problem I see is anti-"nazi" rhetoric quickly descends into dehumanization rhetoric about how such people don't deserve to live, should be ejected from all civil society, and must be relentlessly persecuted by every legal and social mechanism possible; in fact, all the suspension of every civil right is acceptable if it means stopping nazis. At the same time, it seems that almost everybody who lived in 1940 would be considered a Nazi by today's rather loose standards, and everybody tries to paint their opponents as nazis (even conservatives have the rather inept 'actually, Nazis were SOCIALISTS" retort) and apply this sort of rhetoric to what even 10 years ago was a completely mainstream liberal.
Certainly 4chan is full of reprobates of every flavor. But if you live in a society where the existence of Nazi rhetoric is actually dangerous, well, you've already lost your free society. People don't read deranged Internet rants and become mass murderers unless they were born in raised in an already broken, atomized society. The ideology is the excuse for the violence, not the cause. And unfortunately, this sort of rhetoric (we have to do whatever it takes to stop nazis) is also indicative of an worsening social environment.
And typically, in worsening social environments, where a variety of ideologies become excuses for broken and/or desperate people to become violent, the government will become more and more totalitarian in response. And we’ll cheer it along.
And then all you have to do is define "everyone who disagrees with me is a nazi" and you've got not only full-blown censorship but also the moral high-ground!
I know, I know for the sake of appearances we don't define everyone who disagrees with us as a nazi, that would be too obvious (although we still do alot).
We describe the broad spectrum of perfectly main-stream, otherwise unremarkable views (but that disagree with us) as "nazi supporters", dog-whistlers etc.
If someone is stupid enough to fall for the lackluster logic of Neo-Nazis then I see that as a problem with our public education, not with the moderation policy of a website. Sure, enforcing "correct" speech at all times could potentially lead to more harmony in society, but I would much, much rather invest in empowering people to think critically for themselves. Many are already able to resist the persuasiveness of propaganda, ads, conspiracy theories, and extremist groups that are all around us today. Teach this skill of resistance instead of trying to baby-proof society.
