From Harry Potter and Methods of Rationality, slightly edited to avoid unnecessary spoilers:

"So now I've got to find some way to kill an immortal Dark Wizard," he said, and sighed in frustration. "I really wish you had told me that before I started shopping."
"There is no justice in the laws of Nature, mister, no term for fairness in the equations of motion. The universe is neither evil, nor good, it simply does not care. The stars don't care, or the Sun, or the sky. But they don't have to! We care! There is light in the world, and it is us! "
I'm not a psychopath, I'm just very creative.
If I am not too young for moral judgment, then neither are they. No, mister, they didn't deserve to die. But they did deserve to be stripped naked and glued to the ceiling.