He could have shot into the air, he could have used non lethal weapons, something like that.
He did. But Iraqi's aren't afraid of that. They shoot in the air for every reason (or no reason at all).
War mustn't be an excuse for anything.
To some extend. You want to put war into rules, but you'll see it's impossible. No side will totally obey these rules. It would be nice if they did, but it's not gonna happen. That's reality. It's unfair sometimes, yes.
There are strict rules and laws which explicitly define whether a murder happened in self-defense or not.
How can you oversee events in the heat of battle? That's difficult. Sure, when one murders trough brutality, I'd say punish him. But if it was self-defence or accident? The question here is: how do you know exactly what and why it happened? The rules are clear. The situation is not.
This sounds like "Do what I order, or you will die!".
More like: "don't steal, or face the consequences" to me.
If a marine kills people without an urgent reason, he must be punished and banned from the military. That is the only just thing.
I agree with that one.