Dude, seriously?
I think some of the most vocal homophobes in society are actually repressed gays. They don't want to be around it because they're afraid they might like it.
If theres gay in your heart, let it out bro.
On a serious note though, I seriously doubt anyone with HIV or full blown AIDS is going to be in combat. The way they screen you for things in the Army it seems like that is something they'd catch right away.