Do you think this also holds true for americans who develop weapons to kill people? American drone pilots dropping bombs on cities? Palantir employees, bank employees, lobbyists, people working on DRM and censorship systems, politically partisan reporters, etc. etc. etc. etc.

I find this hand wringing around Facebook employees very wierd when it's so trivially obvious to find people that outright build systems for murdering other people and are even proud of it. If those people exist in hundreds of thousands, why is existence of people that build a webpage that sells advertisements and shows messages from people this wierd? In what way is it worse working for Facebook than working for a news outlet to write fake news that outright attacks LGBT communities? And why can everyone understand existence of those reporters and then wonder why people still work at FB?

I suspect weapons-manufacturers and soldiers are less self-deluded, to be honest. They believe there are bad people in the world who need to be killed to keep America safe. They also believe in the principle of civilian control of the military, and it's not the military's job to second-guess the elected leadership of the country. Who specifically gets killed is above their pay-grade.

Contrast this with many FAANG employees who may believe they personally are "making a difference" and continually second-guessing and sniping at their (unelected) corporate leadership because they need to feel that they're On The Right Side of History.

You are contradicting yourself a bit in your second paragraph. Employees who want to be on the right side of history have stopped Google from doing projects related to weapons and Chinese censorship, which is literally making a difference.