The Marine should have walked away and chalked the experience up as a lesson learned.
I was in the Marine Corps as well and was accosted by prostitutes whenever I left the base. But I never partook. The whole scene just seems kind of skanky to me.
What's wrong with meeting a nice girl in church or at the library and then courting her like a normal human being?
There is no excuse for the murder unless the man was trying to force himself on him. Even if not, to present yourself as a woman (when a man) to a man, with the intent of having sex, should be considered sexual assault. Even if all it is is kissing, it is not with consent because of the deception.