Can you really blame them for trying? It's not as though they can see history. Without knowing that their beliefs were inaccurate, they fought to convince others to believe the same things. They ran wild in the nights, butchering their neighbors for committing the crime of nonconformity. They never stopped to think what would happen when the crusading ideologues had nobody left to attack. They were surprised to find their bloodthirsty norms turned against them, imprisoning their minds and making them fear the act of thinking any thought which contradicted their beliefs. Two generations lived with this fear, but only one was able to live without it before another attacked the world with a new belief.
I often find myself standing up for people who believe horrible things. I don't stand up for them because I agree with them: I stand up for them because, in many cases, their beliefs and verbal actions should not be grounds for the suspension of their liberty.