Harry to Dumbledore in Ch. 39:

"... look within the part of yourself that flees not from death but from the fear of death, that finds that fear so unbearable that it will embrace Death as a friend and cozen up to it, try to become one with the night so that it can think itself master of the abyss. You have taken the most terrible of all evils and called it good! With only a slight twist that same part of yourself would murder innocents, and call it friendship. If you can call death better than life then you can twist your moral compass to point anywhere -"