“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?”
Alexander Solzhenitsyn, who knew about evil, expressing what I consider an axiom of realist morality to be believed even when one perceives evil in a group as surely as one perceives light. (From Self Doubt)