An enormous pile of swiss cheese thinking, psychos like Hasan exist everywhere in all cultures and all societies, but they do not define any essential element of humanity especially over time. Hasan is that horrible combination of religious fanatic and grievance obsessed lunatic. Given a large population they are rare but there, given the right situation they act out their evil. Advertise for them I'm sure you'll find many.

Interesting piece on evil.

Philip Zimbardo shows how people become monsters ... or heroes | Video on TED.com