My only concern is extremists making use of it to organize, spread misinformation, coordinate attacks, etc. and there's zero oversight. That's a serious concern that needs addressing, but I have no idea how.
Ban those communities from your instance. There's not going to ever be any way to prevent them starting their own, all you can do is defederate. There doesn't need to be any more.
Yeah, same thing that happened when gab started a Mastodon instance, everyone immediately defederated from them for being Nazis and their reach stayed confined to only their own platform. Deplatforming is never completely stripping a platform from a person/group, it's more of a quarantine. Keep them isolated from the wider community so they can't recruit new members, and their groups wither
I mean, if it's real bad shit like violence, that's where FBI comes in, right?
Not sure if the ACLU would be able to do anything about hate speech.
But bad actors would have to run a shell game of go between instances to recruit. And they've been doing that shit for decades anyways. Hell, it's the same thing as under 18 punk shows back in the day when nazis hung in the parking lot trying to give booze/drugs to kids.
Like, imagine if someone said we can't have phones because assholes can also buy a phone...
Any extremist group can get a server and start a forum, and talk however they want. The point is not to try to censor them, but ignore their instances/users, so it becomes it's own bubble (same thing as them having their own forum).