Jesus, I am a Chritsian, I don't think people are just born homosexual, I am also a 20 year military veteran. Just let them serve. Seriously, will there be a few who try to grab ass and such? Sure there will be, guess what, there are some women who try to play grab ass with men, and lots of men who try to play grab ass with women. But by and large we're a professional military and very few of the grab assers stick around long.
In my personal opinion homosexuality is a sin, but it is not a crime and shouldnt' preclude anyone from serving if that's their desire.
I've served two tours in Iraq, one tour on the Mexican border and several deployments in the state of Arkansas and I call tell you, I never not once thought "gee I wonder if the dude next to me is gay."
Let em serve openly, who cares?