By all indications, Mr. Sites was a professional, doing his job.
In any case, Mr. Sites is not the one on trial here. He's not going to be judged by his fellow soldiers, as to whether his actions stained the reputation of the Marines and that of the United States of America. If the evidence suggests that the soldier obeyed the rules of engagement and is innocent of wrongdoing, then his peers can certainly make that call.
The price of standing on the moral high ground is that sometimes you're a more visible target. Those who would argue that the Marines should sink down to the level of our enemies should consider whether such a course of action saves lives in the long run, and protects the honor of our Marines and our nation.
Who said that the moral high ground doesn't come at a price? Brave warriors stand tall.