http://www.cnn.com/2007/WORLD/meast/...ing/index.html
The first part made me think, well, maybe it isn't all bad that the US went over there and whatnot, shit like this shouldn't happen. Then I continued reading and it says...
"The killing is said to have spurred the killings of about two dozen Yazidi men by Sunni Muslims in the Mosul area two weeks later. Attackers affiliated with al Qaeda pulled 24 Yazidi men out of a bus and slaughtered them, a provincial official said."
To me that shows that they take care of things in their own ways, and you're not going to stop them all. One part stepped out of line being idiots, and another part retaliated in response to make it deathly clear that shit won't be tolerated. To say that's barbaric or whatever, well, what would you want the US to do about it other than retaliate too? Calmly explain, hold lessons? Perhaps we don't examine enough how they handle things. People don't love to go around fighting all the time for no reason.