True, but it's only a matter of opinion who "starts" the war, and who simply defends themselves. If America up and attacked a part of Canada, Canada would have a right to defend itself, correct? So there would be two ways of looking at it--either you support the Canadians, and say "Well they were attacked, they should defend themselves", or you blindly support the Americans, and say something like "well that land was rightly theirs to begin with", or "it's just a counter-attack for years of oppression", or something equally ignorant. As is happening with the current War on Terrorism. But, hey, that's off topic.

Genocide would be the worst crime, but on a more common scale, I'd have to go with rape, or more specifically, child molestation.