> Is it possible to bring fringe groups back into the fold of peaceful civil discourse

It's not really "fringe" groups that are the issue here; it's "extreme" groups - no-one is calling for the flat earthers to be deplatformed, for example.

> Does censorship, even if justified, fuel anger and distrust

Probably but I'd guess only among the people who are already inclined that way already.

> the population must always have their speech regulated

If you put "some of" after "have", it's the situation we already have.