As a member of the USAF, I'd like to take a moment to address some of these concerns.
1. All military personnel have mandatory medical screening for many blood-borne infections every year. Individuals infected with HIV are on a strict drug regiment. Like persons with diabeties, they are rarely removed from duty (read: kicked out) but are instead placed on restricted service. They aren't allowed to deploy down range because they could (a)become wounded and possibly infect others and (b)run the risk of capture and running out of much needed medication which risks complications.
2. It's very sad that rape is an actual problem in our military and that it goes very under reported. That said, there is no reason to believe male-on-male rape would increase. Implying guys getting hit on by other guys is even remotely like rape shows vast ignorance or willful hate on your part. "No," will be sufficent to get a guy to stop hitting on you.
3. There is, unfortunately, the increased risk of violence against homosexuals once they start coming out of the closet. I work with several self-described "good-ole boys" raised in the midwest that openly claim "them gays ain't going to come out 'round me or I'll beat 'em." *Actual quote* But like sexual assalt, racial discrimination, religious preaching, drinking and driving, and a plethora of other issues, we will get to sit through a very long and boring powerpoint presentation telling us what not to do, what to do if we see something wrong, and how to report it.
4. Favortism? Really? The evaluation system utilized by the Air Force (I can't comment on the other services because I have no experience with them) is top heavy as is. There is no illusion in the ranks that the system isn't broken; we just make due with what we have until we get around to trying to fix it again. It is so much harder to write a bad report that most NCO's just inflate bad troops to make them look good and have an easier eval to write. Take all this into acount and favortism for or against homosexuals won't play much into it. If anything, gays won't get their desired assignments or cool overseas jobs (Japan, Germany, etc.) as such positions will go to good, straight people.
5. I hear this all the time. Those that leave either are planning to get out anyway or are increadibly short minded. Most of the old corp still around that say this won't leave because they haven't reached 20 years of service to retire. They want their benefits so they'll suck it up. They'll then either realized how stupid their position was and keep serving or get out (after retirement benefits activate) claiming "the gays ruined the military." The few similar minded in the younger generation that haven't commited more than 6-8 years already will get out and move on to other jobs. Other than their fantasy football league, few will likely miss them. As too the weakened state of the military: I'm fortunate enough to be a close friend of a serving homosexual. We've spared many times in unarmed combat training and he kicks my ass every time.
I served 2 years in England. The base's Marine detachment was taking being trained by a retired SAS officer.
To the posters on FSTDT, thanks for your support of the troops. I know we all appreciate it.