Not to mention the collateral damage to society by concentrating the most active users in these communities into off-site echo chambers.
But if that random person is removed from Twitter and starts seeking out like-minded people, they're going to form some underground community with no pushback against the worst ideas.
2) Since you seem to hate Nazis so much, why are you adopting the digital equivalent of their tactics? The Nazis famously burned lots of very Jewish books, right? Society used to say that this was one of the examples of why they weren't so great, and I grew up hating the idea of burning books because of this. I can't understand how using their playbook suddenly became doubleplusgood.
That's a real population of extremists. Having them hang out on HN does not make their numbers dwindle.
And no, I do not think that banning Nazis from forums is "the same playbook" used by the Nazi Party.
I'm always open to at least talking to anybody, whether or not they're ISIS members, Nazis, Communists, or (may Allah forgive me for even uttering this word) Canadian.
Talking is the road to peace. When words stop, there's only one thing that can possibly come next.
You are free to go to their spaces and talk to them if you want. But there is no moral need or practical good to permit their hatred in all spaces.
What if the more important metric for a good society was something else?
What if removing "the bad guys" from society makes them feel like they're not part of society and have nothing else left to lose so it actually pushes them to violence?
I'm not saying I have all of the answers here, but I do strongly think that your general approach here is ignoring the human side and focusing on the wrong metric for progress.