If this, from the CNN story on the shooting of civilians at Fallujah, doesn't send a chill down your spine, you have no human feelings:

One U.S. Army sergeant said he shot at what he saw, "and what I saw was targets. Targets with weapons, and they were going to harm me."

"It's either them or me, and I took the shot, sir, and I'm still here talking to you," he said.