I disagree. Even if the boss found somebody else to do it, the fact that somebody had stood up and said no would make a difference. It still would provide an example to other employees. Behavior is contagious. You have more power than you think. If everyone sits back and says "I can't act ethical until we have big political and social changes", I can guarantee you that those changes will never occur. Somebody somewhere has to start the ball rolling, even at some personal cost, or nothing will ever change.

It sure would provide an example to other employees. Mike was replaced because he wouldn't write the code he was asked to write. Lesson learned: Write the code you're asked to if you want to keep your job.

>If he hadn't coded it, someone else would have.

At his level at the time, sure. Anyone can write a web quiz. But I would think that a lot of the most significant ethical challenges developers face would be in much more specialized areas.

Safety-critical systems often have real-time and embedded components, for example. The regulations for safety-critical software vary a lot between industries, too, which makes it even harder to find a replacement for someone who leaves for ethical reasons.

if he didn't murder the guy, someone else would have

well you can all down vote me, but we could all decide to just be nice to each other, we have enough tech and resources to house and feed everyone in the world

If we lived in a society where murder happened on a massive scale, that might not be an absurd statement. Imagine if we treated humans the way we treat farm animals for instance..

That being said, sometimes (more often than not?) acting on principle and making the strategically best decision for the world, align, so I'm not saying one should never act according to principle.