Fb's research in computer vision has produced works like training a neutral net on large datasets in 1 hour, instance segmentation neural nets, and many more, and made the code and research public with nonrestrictive licenses. These are pushing the state of art! Check out the work yourself and then come back and criticize these scientists if you feel that their work is a net negative on the world.
The question as you so rightly point out is whether there is a net value added.
If we took their AI contributions and JS frameworks on one side of the equation, do you really think it balances the other side of the equation?
On that right side lies encouraging general disinformation leading to broken elections and even aiding genocide. Academic studies on happiness show using Facebook and Instagram correlates with poor mental health; that research has been replicated.
What product actively damages those that consume it?
Facebook is the digital equivalent of the Tobacco industry; good business that's bad for people.
