It's really a beautifully simple and true statement. Hate simply cannot fight hate. Maybe some people are not meant to change in this lifetime. But if anything can help them, it's love. I really believe that. There should be consequences to actions if we want to incentive certain behaviors in society. But consequences don't require hate or even anger.
Hitler may not have been destined to change. But what Daryl Davis does is show these people love. And if you've changed the lives of 200 KKK members - believe me, you've seen it all. You'd be hard press to cherry pick only the nice 200 KKK members.