You forgot one major thing. The algorithm. Facebook decides what you see and what is being recommended to you. If they recommend to you something that has more engagement but is fundamentally false, we have a problem. It's one thing when it's just a pure communication platform (whatsapp), another when you push/promote some content in the feed over something else. No they don't have a master evil plan, but they are careless and don't care about their own responsability. One example where it becomes a problem: it was proven that there was violence in Myanmar triggered by false information that was pushed by the algorithm to more people
That's very fair criticism, and you're right, promoting something to others based on the probability of it triggering a reaction has some pretty major downsides. Although I don't know the specifics of Facebook's algorithms, from my experience, I would agree it seems to amplify posts trigger an emotional response, e.g. "oh, that's so CUTE!", "oh, that's so COOL!", "oh, that's so FUNNY!", "oh, that's so TERRIBLE!", etc.
I guess the only thing that I can say is that it may take a while before we have AI that is capable enough to distinguish baseless posts intended to stir people's emotions from those which may have merit but are emotionally engaging and controversial. In the interim, it seems like Facebook is trying to brute force solve this with human moderators - but again, perhaps not the most objective way of handling this and I wonder how they will tackle this long term.
(On a different note, I'm being throttled by HN for posting too fast, so sorry for the delay in response).
