Yeah, I don't have a complete answer here. I think that Terms of Service requiring standards of behavior are quite reasonable - people in Congress, for example, are required to conduct themselves to a certain standard or be ejected. Same goes for courtrooms.

There may be a "minimum threshold" for content or communities that are blocked, on the basis of materials provided (hate speech, harassment campaigns, doxxing, CSAM), but I'll readily admit that this is conjecture.