I'm sure that few Americans today would defend what occurred at My Lai, just as they did not try to defend it at the time. From all accounts, it was a gross misuse of power and soldiers basically losing control. That said -- and this is not an attempt to excuse, but rather to understand -- I think part of the mindset involved is that these men were traumarized by their war experiences. When you live daily with the prospect that this day could be your last . . when you see comrades and friends severely maimed and killed . . . when you see such attacks against you committed by women and children (as reportedly did occur) . . . it becomes easier to see that soldiers (being human) can have that stress build into rage and not thinking clearly.
Lord knows, when I watch real-life crime shows and I see questioning of rapists and killers who non-chalantly, even glibly, recount their horrific crimes against the most innocent of victims, I don't know what inner restraint the detectives have that keeps them from leaping across the table and gouging these guys' eyes out with a ballpoint pen. Not even knowing the victims or their families, and just hearing the gory details of the crimes, I would have no problem carrying out a death sentence on the spot. Imagine how living with daily risk of death for yourself and your buddies, at the hands of people who look like the citizens you're trying to defend and protect, must affect a person. I just don't know why more atrocities like My Lai don't occur. I admire the extreme restraint that most soldiers possess.
You could argue that the Vietnam War, as with Iraq, should never have happened. The fact that they did happen set into motion the things that resulted, including atrocities. You don't put soldiers in a police-action mission (as both were/are), leaving them as sitting ducks, without seeing the potential for excesses grow with the passage of time. Police actions don't work. If U.S. cannot go in and blow the place up, then pack up their gear and leave, then we shouldn't even go in. Of course, this means hardly any military interventions would occur, but I think that is the only feasible way to take action and minimize fallout. Or, maybe next time (as I've posted before) we need to allow other countries to take the lead and show us how its done. I do think it looks easier from the sidelines than when you are playing the game.