This seems out of touch with the reality of these large firms. Management is pretty distributed, decision-making is distributed, and your manager is likely also an engineer, or used to be one. Many people work on tools that are general-purpose, in different levels of the stack. Someone working on keeping the data center running doesn't deal with what the applications actually do.

Also, people change positions fairly often and avoid work in areas they consider to be unethical. This means that the people in a position to actually make the call are people who don't find it unethical, because the people who would be concerned about it avoided the whole area. Like, if you don't want to work in ads, you'll probably find a job in some other division, or at least not directly on something you consider unethical. The people who came up with AMP (to pick something controversial on Hacker News) were true believers who sold it to management.

But people still care about the company's reputation as a whole, and as a result you get conflict between the people not actually working on the controversial thing and the people who are, but that mostly results in a lot of drama and cynicism.

The politics is complicated. I can't think of a generic oath that you couldn't rationalize your way out of.