This... This is not helping. I am not sure what sort of impetus made this young man decide to do what he is doing but he is wrong. Well meaning or not his actions are at the very best intimidating and at worse moronic. This is not the impression responsible gun owners want to leave with the general public. Moreover he seemes to indicate that he wasn't prepared to shoot anyone.
So then why carry a gun openly? Purely the false theory that a gun is a magic talisman that will ward off evil. Open carry has not been shown to effect criminal activity in any significant way. Of course it will deter some crime but overall the determined criminal is not worried about some pencil neck geek with an AR15. Especially if he doesn't have the cojones to use it.
His "brief" time in the military can only indicate he was morally,mentally or physically unfit for duty. This sort of open carry buffoonery is what makes the general public think that "reasonable" restrictions on firearms are, well reasonable. We are shooting ourselves in the foot with these kind of displays. Pun intended.
If this young man wants to patrol his neighborhood and fight crime. I suggest he volunteers for public service. Become a law enforcement officer, become a EMT, try the military again. Whatever he does he needs to quit being "that guy."