"They" is unnecessarily vague I guess. It's not fair to write off the entire population of Facebook staff... There are surely a substantial chunk of employees who were entirely unaware of these tactics.
It's easy to claim an organization is evil. Less so for individuals, and with good reason. There's something to be said for remembering to humanize people, even those most "undeserving."
There is no harm in me saying out loud "Facebook is an evil company" even if I'm completely wrong, because they are so powerful. It would valuable for everyone to scream at Facebook at being evil because that would force them to show and prove that they are not.
We shouldn't get stuck on being "accurate." Throwing rocks is not just okay, it's a good idea if it forces the powerful party to act/respond.
As for the individuals -- it's their job to defend the company. If that hurts their feelings or whatever, too bad. I don't care and neither should you (presuming that Facebook is potentially very harmful.)
And no, I can't give you a clear brightline test right now to determine this. It takes homework.
But.
If you want to A/B test whether people prefer blue chewing-gum to green, be my guest.
If you want to A/B test for literal depression and sell stuff to people based on that, you're probably evil.
The line's somewhere in between there. Now we know where Meta has chosen to go on some of this; and again, this is from WHAT IS KNOWN TO BE PUBLIC.
The safest thing is to assume the worst, then. May they rot.