Power to the people.
As to "many cases where online communities document or facilitate crimes elsewhere", why criminalise the speech if the action is already criminalised?
That leaves only "Campaigns to harass individuals and groups". Why wouldn't moderation tools as powerful as the ones employed by Twitter's own moderators deal with that?
[1] https://mtsu.edu/first-amendment/article/970/incitement-to-i...
That is, it's not clear in the US you can ban something on the basis of it being immoral, you need to have the justification that it is "documentation of a crime".
This does not stop the FBI from being a major child porn distributor, despite that meaning the FBI is re-abusing thousands of victims under this rubric.
That's what makes it illegal? What if it's done on a private forum that the victim never finds out about? What if the victim is, say, dead? I don't think those change the legality.