This is nuts.
Both were being immoral, one was self-deluded as well.
Everyone involved was a sinner. Thats no excuse for yet another sin.
Killing or even violence that risks death is wrong unless there is a physical risk. The Marine fell into the temptation of rage, resulting from an offense against his pride. Pride, of this sort, is a sin. Rage, of his sort, is another sin. That is as much a trap of the Devil as the delusion of sexual confusion.
Amen