I suggest that some of the posters on GC should try to find a copy of the un-edited video of the incident... you can watch the unit enter the Mosque in open order (ie. not tactically), watch them move around the room securing the area, listen to the Marine in question make jokes about the prostrate man faking being dead (ie. he's still breathing), then raise his rifle and shoot him, then make a follow-up joke (ie. he's not breathing anymore)...
This might remove some of the misguided attempts to explain away the Marine's action.
Here is a link to the BBC site that had the video:
BBC
http://news.bbc.co.uk/1/hi/world/mid...st/4014901.stm