There will be violence. Most men don't want to be "eye"ed by another man who is attracted to other men. I witness such violence when I was in the military.
 Disciplinary action on enlisted men will rise, costing the military good men and curtailing the potential careers of those who would otherwise stay in for the long haul. It's too costly to send men through basic training and advanced schooling to squander it on the battle of sexuality in the barracks.
 The reputation of the military will suffer and people will think twice about joining. Parents will be concerned that their teenage son will be subjected to close quarters with homosexuals at an impressionable age.
 It sets up yet another identity group for soldiers to "belong" (it's bad enough with the races and religions...now sex?).
It will be just another stab at core cohesion, and American citizens owe it to the enlisted men to improve conditions, not make it worse.
If the majority insists that gays be out in the open in the military, gays should be segregated just like the females, from the living quarters of our normal enlisted men. It's essential to keep sex out of the barracks.