And? Other people's immorality does not excuse one's own. Other people kill and steal, that doesn't mean that I should do it anyway because other people are going to whether I do or not. That just makes the world, and me, worse.

"They'll find someone else to do it, so it's okay for me to do it" is a classic example of flawed and immoral ethical thinking. We could go for broke and add in "I was just following orders" and "But I didn't know people would die"