https://en.wikipedia.org/wiki/IBM_and_the_Holocaust
The clear answer is that one should never just be following orders and if your company is doing something that you personally feel uncomfortable with, you should try to stop it. And failing that, quit.
It certainly would have been better if we could have gotten US policy on Nazi Germany to change much earlier than it did. It would have solved the coordination problem--for US companies, anyway. This would have required direct political action.
> Harry Truman, was quoted in the pages of New York Times in June 1941 as saying, “If we see that Germany is winning the war, we ought to help Russia; and if that Russia is winning, we ought to help Germany, and in that way let them kill as many as possible …”
So what? You might as well be a hitman because, if you're not, somebody else will. You're just leaving money on the table by not being a killer for hire.
Your own principles don't depend on what your competitors will do.
That specific point was about the importance of using your political power to act as a group in a way that will actually affect the world, rather than solely appeasing your conscience/principles.