As far as "understanding why they do it", here's a lesson I've learned along the way: cultures and religions may vary wildly, but people are very much the same all over the world, with the same general range of personalities, wants, needs, desires, and dreams.

The regular people of North Korea are every bit as good as those of any other nation's population...but who are having to do their best to survive under a tyrannical regime.

If you haven't had the chance to really experience other cultures on a deep level, I strongly recommend the works of Aleksandr Solzhenitsyn (esp. The Gulag Archipelago). They're long and can be a bit of a slog by today's standards, but they're filled with insights on humanity, motivation, and thought processes, and may help you realize just how alike we really are.