In addition, besides anonymity, people are far worse online because there is no real person they are interacting with. They are interacting with a caricature of a person they've built up in their heads based on a highly limited set of information.

Finally, you lose all sorts of body language, tone, and other cues, that prevent you from actually interacting with someone, and instead has you interacting with your vision of them, which is highly influenced by your emotional state and preconceived notion of what you think they're saying.

I don't think it's reasonable to put the blame on the users. Facebook in particular, creates that caricature in order to increase "engagement".

You will not see a representative sample, much less all, of your friends posts if you use it normally. If two people make one in 20 posts that are outraged, anguished, political, Facebook will probably show them only those of each other, which creates a feedback loop.

People talk about possible future "paperclip maximizer" AIs overwhelming society, but Facebook is essentially doing that right now, only it's "engagement" instead of "paperclips".