[Bolds mine.]
Disobeying an order as "unlawful" invites prosecution and hopefully due process (and lets not be hypocritical here, the U.S. was willing to hang those who committed acts of war that were policy in Nazi Germany and Imperial Japan who, if they had disobeyed their "orders" would have invited a bullet sooner.)
I'm not really a WWII buff, but I didn't think we hung junior infantry officers who fought against our soldiers on the front lines. Also, there were huge protests about the entrance of our forces into the European theater. But people back then had a stronger sense of national pride and duty, so they did what they were asked by their government, and it turned out to be the right thing.
As far as the legality of the order to go to war in Iraq... Historically, it's an interesting dilemma, because military officers (usually higher ranking commanders) can be held accountable for their actions, even when following orders from the president. I think everyone wants us out of this war in Iraq, but nobody knows how to get out of it safely. The solution is not for some cowardly infantry officer to try to weasel out of his obligation by claiming that a declaration of war is illegal. You can argue the finer points of his decision, but I think that the decision to go to war is now a general order, and it's not really up for interpretation by junior officers. I have zero respect for this guy, and I think he is either (a) long entrenched in a media ploy or (b) just scared and I don't believe his claim that he would willingly participate in a war in Afghanistan.
I don't know the details of his "missing movement," but it's important to take into account the ramifications of this. Let's assume he was a platoon leader who had been training with his platoon for a year before deployment. Now that platoon has a new leader who is not familiar with their strengths, weaknesses, and personalities. From his actions, I imagine it was good that he was not with them, but now they are conducting combat operations with a new guy and therefore increasing their risk of harm. If he was an officer worth his salt, he would have deployed with his guys, led them, trained them, and made sure that they did the best and most honorable job possible given the circumstances. Then he would have come back and made his case.
West side, I disagree with your points, but I think that it's difficult for non-military people to really understand what it's like to serve in the military, especially in combat. Very few people ever want go to war, and no platoon leader will ever tell you that an objective is worth losing one of his Marines' lives. It always seems criminal when one of your guys is lost trying to save some dirty middle eastern country from itself, but they still do their best trying to make sure their guys are set up for success. Really, good military leaders don't do what they do for the political objectives of their country. They do it to try to keep the politicians from getting their guys killed. This guy is not of that ilk, and he's a coward. I think the best course of action would have been to get him out of the way as fast as possible and move on. He knew they wouldn't do that though when he made the "unlawful order" claim.