I think a lot of fear is rightly grounded in history: it's clear that this much power in very few hands turns to shit at some point. Facebook may well be humanity's biggest concentration of power (knowledge being power). How do you keep an advantage when the other side knows >> than you could ever know? There's also the disparity in availability of AI, since large applications need powerful and thus expensive hardware.

To be clear, I don't think Facebook is flawless. All the issues you bring up are definitely true.

I just think it's unfair to assume that these issues automatically make Facebook evil and that there's no good they do.

They certainly could do good, theoretically. Problem is their business model, because manipulating people doesn't fall under "doing good". As long as they make profit by selling people, they're the opposite of good because their activity goes against peoples' interest.