There is a tendency [...] to talk about figures like Hitler and bin Laden as beyond human understanding, as a dark force that just sprang full-born into the world. [But] evil has nuances -- it doesn't just emerge in its full nightmarish quality instantly, it develops day by day, it has its own evolution. That makes it more horrific. Because if evil were something absolute and distinct, it could be removed from human experience. But it's not, which means we must come to terms with how it arises.
And last month:
It's easier for me to sleep at night if I think that perpetrators of genocide and mass killing are lunatics or insane or only found in cultures like Germany. I don't blame people for jumping to those explanations. But for me it begins with the issue of numbers. [...] If you want to say that the only people who do this are lunatics or insecure, then I just don't know if you can round up that many people like that in a given society to commit the scale of atrocity that we see in genocide. You simply can't rely on the fringes of society to do that. A lot of ordinary people are going to have to be recruited into that effort as well.
That does not make evil excusable or justifiable. Of course it doesn't. But it means we must remain vigilant not just against some indefinable "other" evil out there somewhere, but also against the evil within ourselves, because it's always there, beneath the surface, somewhere in the world. Because ordinary people can do evil things, it may be something we can prevent -- at least sometimes.