IDK I feel like that shouldn't be the main lesson to take out of this. I've never been in the military so I'm mostly talking out of my ass, but historically this kind of stuff happens in every war, to everyone. I assume when the shit hits the fan and you're fighting for your life day in, day out, the difference between a "legal" and an "illegal" order becomes pretty difficult to think about. It's horrible and people should be punished for it, but I don't know that training on the legality of wartime orders is going to help.

On the other hand, all those higher ups who covered up the massacre and tried to create a narrative to save the reputation of the Marine Corps? Fuck those people. IMO the cover up is much worse than the crime. Without accountability you don't know how many more of these massacres may have happened.