Alexander Solzhenitsyn.

“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 dividing line between good and evil cuts through the heart of every human being, and who is willing to destroy a piece of his own heart?”
-- Alexander Solzhenitsyn
The Gulag Archipelago, (New York: Harper & Row, 1974) vol. 2, “The Ascent.”