My guess is the person is a troll.
No, my guess is he just doesn’t like “girls” in the Marine Corps. I’ve run across these types on FR from time to time. (Said as the proud father of a FEMALE Staff Sergeant US Marine Corps, whose brother just got back from 7 months in Afghanistan as a wizzo on a Mud Hen.)
The standing joke in our family is that if those two go into a bar late at night and get into a jam, she will probably be the one that gets them out of a “problem”, not the son.
I suspect this guy best not cross her either.