^ We'll obviously the ouster of Saddam created a power vacuum and we all know the post major military operations administrative planning was a failure. The power struggles, revenge killings, outside interference by Iran, al Queda, and others plus religious differences are the root causes of the civil strife.
Occupation plays a role but on the grand scale of things it's less responsible for the infighting than those items listed above hence the fear of a bloodbath if a quick withdraw is done.
Obviously your soldiers are criminal murdering psychopaths who take great care to shoot kids in the head.