Jack

“But would you kindly ponder this question: What would your good do if
evil didn't exist, and what would the earth look like if all the shadows
disappeared? After all, shadows are cast by things and people. Here is the
shadow of my sword. But shadows also come from trees and living beings.
Do you want to strip the earth of all trees and living things just because
of your fantasy of enjoying naked light? You're stupid.”
― Mikhail Bulgakov, The Master and Margarita

“Animals don't behave like men,' he said. 'If they have to fight, they fight; and if they have to kill they kill. But they don't sit down and set their wits to work to devise ways of spoiling other creatures' lives and hurting them. They have dignity and animality.”
― Richard Adams, Watership Down

“People who claim that they're evil are usually no worse than the rest of us... It's people who claim that they're good, or any way better than the rest of us, that you have to be wary of.”
― Gregory Maguire, Wicked: The Life and Times of the Wicked Witch of the West

“If only it were all so simple! If only there were evil people somewhere insidiously committing evil deeds, and it were necessary only to separate them from the rest of us and destroy them. But the line dividing good and evil cuts through the heart of every human being. And who is willing to destroy a piece of his own heart?”
― Aleksandr Solzhenitsyn, The Gulag Archipelago 1918–1956