Near the start of Alex Gibney’s documentary “Crazy, Not Insane,” his subject asks the kind of essential question that feels so unanswerable that it is brought up not nearly as often as it should be. Thinking about the nature of evil and recalling her childhood interest in the Nuremberg Trials, she asks very plainly, “How come I don’t kill?” Everyone gets angry. But not everyone commits bloody murder. Barring answers of a spiritual nature, squaring that circle will necessarily involve spending time with some very unpleasant people, which is exactly what the woman who asked the question spent a career doing.