When 4chan did this, they were investigated by the FBI. Reddit received a lot of flack for its own vigilante brigades after a mistargeted attempt to "catch the Boston bomber", and had to take action (still incomplete) against raiding.
Facebook and Twitter with their multi-billion market caps have just barely begun to wake up to what their platforms are capable of producing. The effects observed with these investors are not exactly unique to tech finance.
I think something like Wikipedia's protected article policy could help. When something becomes problematic, discussion can be limited to confirmed users, who in turn have more to lose by being banned. This allows Twitter to respond before "censorship" is justified.
It feels like Twitter's user base is much more radical, and the focus of the product on instant public messaging might add fuel, while Facebook's group system generally limits the spread and seems to be more geared towards asynchronous sharing (+messenger, but that's more of a chat, not public).