I agree with the general principle, expressed fairly crudely, that - good, innovative things (React) can come out of bad places (Facebook, in my opinion).

That's historically true of lots of research innovation though.

War (generally accepted as bad thing!) has advanced technology and civilization repeatedly.

At least the scientists aiding war (on average) had some awareness that killing people is clearly not a good thing, and at absolute best a necessary evil. Can the same be said of the people at Facebook?

The culture of their management is to be in denial about how damaging their service is to the mental health of individuals and society.