An idea i had that i imagine would turn out pretty well is Japanese speaking forums for westerners specifically. It'd have a buy in that no one interested in only trolling would go in for (learning a language, especially one far from English).
Some pirate coves protect themselves by requiring an invite from someone already in the community, that could work really well too.
Generally, just requiring a little work to get someplace would make communities a lot nicer.
In spaces that are both liberal and political (or adjacent to politics) I'd say he's correct, but generally I'd say a cult of toxic positivity would be a bit more broadly applicable.