I'm not sure that's true at all, lots of fringe views gain traction on Twitter. I'd imagine more of them still are moderated out of existence.
> So this is the key tension. Outgroups get criticism of themselves every-bloody-where
Yes, and by being a digital town square, Twitter, or any similar platform, would become part of everywhere, with the same consequences for outgroups.
> provide an opening for an outgroup to issue its own civilly-expressed criticism
I agree that outgroups should have this opportunity, but it must be applied to all the outgroups, including those who have a mutual loathing for each other, and those whom we loathe ourselves. Fairness dictates we shouldn't play favourites, in the same vein that the ACLU defended the a Nazi group's right to march through Skokie.
If an outgroup wants a private, safe space to express themselves, that place cannot also purport to be a public square of free expression. It's one or the other.
That's not particularly close to what I said. I am talking about the outgroup being able to participate in the "public square of free expression", in a way that is actually free for them to speak to the ingroup.
These conditions do in fact represent "actual" freedom. Basically if you support people insulting and ridiculing Nazis (which I do), you should support them insulting and ridiculing anyone else on the same principle.
> civilly-expressed criticism of themselves and their worldview [0]
or where they should expect to be ridiculed and insulted? And why would anyone sane want to regularly participate in the latter?
As to why people would want to participate, I suspect it's for the usual reasons: to accomplish a goal, or to gain influence and social status.
Edit: Surely you agree that sometimes rudeness is warranted, and that people in fact are rude on Twitter?
> the sort of place that people feel unafraid to discuss controversial subjects?
> If the choice is between some outgroups feeling uncomfortable with civilly-expressed criticism of themselves
So this is the key tension. Outgroups get criticism of themselves every-bloody-where. As you noted, "We're discriminatory, hierarchical, social animals". One more place doesn't make the difference. What good moderation does is provide an opening for an outgroup to issue its own civilly-expressed criticism, with a chance of being listened to instead of reflexively ridiculed and dismissed.