You said:
When is it illegal for a Marine to fight back to prevent himself or other members of his unit from being killed during an attack on them?
My reply:
When it goes beyond the parameters you described, which the guy I was responding to indicated was perfectly OK.
Kindly note what I said. There is a line between the legitimate application of deadly force and murder, even in a combat zone. (For example, you're not allowed to shoot that guy in 3rd squad during a firefight because he wouldn't lend you 20 bucks.) There are indications that this event may very well have crossed the line between legal and illegal, based on the amount of shutting up and lawyering up going on at Camp Pendleton.
My next comment:
If you really want the Marines to be as bad as Saddam's thugs with no adverse consequences
Note the conditional construction. IF you want Marines to be exempt from the laws governing the use of deadly force, then you're saying that there is no law whatsoever, and therefore anything goes, and at that point you're remaking the Marines into something out of the worst days of Saddam Hussein's Iraq. That isn't a good thing.
You know this part..."then you'd best be ready to have yourself a fun and excitingly short life when they get out and become cops in your hometown."
Bottom line these Marines were attacked, they struck back at where they being attacked from, these civilians died not because The Marines were there, but because those that attacked the Marines were there.
Is there some reason why you don't want these Marines to be proven innocent of the charges that haven't yet even been filed against them?