I think one of the main lessons from Nazi Germany (and various old psychological experiments), is that everyday, average, people are capable of horrifying acts. This is especially true for kids who haven't fully developed empathy yet (this is one reason child soldiers are used, gangs are mostly children, etc).

I was around the same age as the poster when 9/11 happened, and had the same thoughts, and many of the kids I knew had the same thoughts as well. I lived in the "country" outside of an all-white, pretty racist, very small town and had christian fundamentalist parents; which probably shaped my views when I was a child. I remember once in school, we had to do a presentations, and one group of kids did a presentation about turning Afghanistan to glass; which got laughs and no reprimands from the teacher.