Speaking as a Marine Corps combat veteran...

Marine corps combat veterans are no more or less likely than the general population to be complete fucking idiots.
Seriously, I knew a guy who was an absolute virtuoso behind the trigger of a S.A.W. If there was a Mozart of light machine guns, it was this guy.
He still had a room temperature IQ and the kind of personal hygiene normally found in barnyard animals.
The Marine Corps, for all I love it, is still a government bureaucracy that does stupid shit on a regular basis.
Combat experience, on the other hand, is just as much a function of being in the right place at the right time as anything else.
Someone opening their argument with either, or even worse, both, is making a weaksauce appeal to authority. Probably because the thrust of their argument fucking sucks.
They're not a pearl of wisdom dispenser.
They're the proverbial guy on the other end of the bar trying to get their proverbial dick wet, and they're checking to see if you'll proverbially buy what they're selling.
If you're down for that, then go in peace.
But try to have a solid grasp of what you're actually agreeing with.
Take care of yourselves out there.