Much of the evil in the world is done by people who are wrapped in the cloak of righteousness such as clerics.  This was one of the messages to the reader in the story, the Bells of Notre Dame.    This message is in the following song from the Disney animation of  "The Hunchback of Notre Dame"  .

Judge Claude Frodo longed to purge the world of vice and sin
And he saw corruption everywhere except within.
Here is a riddle to guess if you can
sing the bells of Notre Dame
Who is the monster and who is the man
Sing the Bells of Notre Dame

    Much of the evil done in the world is done by people who feel justified in doing what they are doing. Common justification techniques that people use are:

1. They convince themselves that the person they are acting against is bad and deserves it.
2. They convince themselves that the person they are acting against is a threat and so they must do it to defend themselves.
3. They discount the opposing opinions of the other person as evil.