I'm not parsing Vietnam, but I will say that William Calley didn't invent Free Fire Zones any more than Lynndie England (can't believe I'm referencing HER twice in the same day...) decided to unilaterally withdraw the US from the Geneva Conventions. Commissioned US military officers swear an oath to the Constitution, precisely because there's no guarantee every order they receive will be in compliance with that highest law of our nation. I don't envy them that responsibility, because it can and occasionally has put them in situations where their only choice is the basis of an inevitable court martial (hence MacArthurs famous statement that it's better to be tried by twelve than carried by six.)

Having said all THAT (which was more than I intended), I don't have to tell you that discipline, especially in combat, remains vital, so the military can't afford to convene the local debating society every time an officer under fire gives an order to eliminate the source of that fire. I don't think the Marines have a monopoly on that concept though. The main thing the Marines have over the service branches is much higher admissions standards based on the fact that their combat role is frequently more demanding that of other services. But, hey, the Army is really good at garrisoning positions the Marines capture.