There is no excusing what happened in Haditha, or it's like in any previous wars, police actions, etc.
Unfortunately the folks that are deserting are prolonging the tour of duty for others and increasing the likelyhood of repeated tours.
All servicemen are schooled that they have the duty and obligation not to follow illegal orders. Of course then they have to prove the orders were illegal (meaning they get to cool their heels in the brig until enough staff can be put together for a courts martial (and it is "Courts Martial" note the "s").
Early out? During a war? I suppose anything is possible but I wouldn't hold my breath. There are many servicemen that are being held over in Iraq and Afghanistan because they have no-one to replace them (critical ratings). The best way out is for someone to "out" you as a homosexual and then give the Sarge a big sloppy kiss. If you survive this encounter this administration will bounce you quickly (causing death and destruction isn't bad for morale somehow, but being gay is, go figure).
Under the U.S. Uniform Code of Military Justice (UCMJ)(which is on-line if you'd care to take a look (p.s. it's pretty draconic)) and the Manual for Courts Martial, any serviceman accused of a violation of the UCMJ that merits non-judicial punishment(we call them Captain's Masts) may refuse the judgement of the officer conducting the mast (no they don't have to be Captains) and request a Courts Martial. A lawyer will not be provided by the military but the accused may hire a civilian attorney to represent him. The Friend of the Accused is just there to ensure that the the rules and regulations of the UCMJ and Manual for Courts Martial are followed supposedly guaranteeing a fair trial to the accused.
Unfortunately it has been my experience that most military personnel who signed on out of patriotism and a sense of duty are most often people who believe everything the administration says. My experience with the people most likely to desert are the ones that signed on for the "free college education", the ones that came into work on their reserve weekends and did nothing but read the newspaper.
There has to be something more than the pay and benefits because they aren't much and are quickly being eroded. The commisary and exchange have been handicapped by Congress and one can now get better deals at Cost Co., Sam's Club, etc. Housing, energy, medical (they actually recommend we get a secondary insurance to cover costs not covered by Tri-Care for our dependents (and no, we don't get lifetime free medical even if it is in print)) and other costs sap the basic pay. Don't even bother to look at the Veteran's Administration!
I wish everyone involved in this a lot of luck, I too will pray for peace and be ready for war.