The thing about moral principles is that they are inflexible. Think about it like the draft during Vietnam. Some people refused to go fight because of moral principle. A common argument against them was “if you don’t go, someone else will go in your place”. Soldiers still go, and the immoral war continues whether you participate or not. I would not go to fight in an immoral war, and I will not politically support a genocide. I know it will happen anyway, but you cannot make me participate. I refuse.