Tsuyoshi is right about something basic here.
Some of the most evil people are the self-righteous ones who can't even see the harm of their actions, and often how twisted their cause is to begin with.
They are in the right so it justifies anything they do.
They are better than others so they can't be judged.
To its extreme, they have the arrogance of being "always right", so anyone who opposes them - or simply disagrees with them - even slightly is an evil to be punished.