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.
As far as I understand in the EU private information is part of the self. Thus, manipulating, exchanging, dealing with private information without the person's consent is by itself a kind of aggression or violation of their rights. Even if the person never finds out.
In the USA however private information is an asset. The aggression or violation of right only happens when it actually damages the victim's finances. So if the victim never finds out about discussions happening somewhere else in the world, well… no harm done I guess?
Both views are a little extreme in my opinion, but the correct view (rights are only violated once the victim's own life has been affected in any way), is next to impossible to establish: in many cases the chain of events that can eventually affect a person's life is impossible to trace. Because of that I tend to suggest caution, and lean towards the EU side of the issue.
Especially if it's the documentation of a crime as heinous as child abuse.