Also, why should we allow fear of violence to keep us from ensuring that everyone is able to be treated fair and equally? Especially in a case like this, where if a homosexual person honestly doesn't want to take the risk of violence against him/her, then all they have to do is not reveal their sexuality to others. The repeal of DADT does not mean that homosexuals will have to tell what sexuality they are. It means that they can tell if they wish to do so without fearing discharge or other punishment, just like heterosexuals now.
I highly doubt that retention or recruitment will go down due to gays being allowed to serve openly in our military. Our military is already turning people away except for certain jobs. And most of the branches will not take most prior service veterans, unless their previous job is extremely undermanned. To add to all of this, our economy is crappy right now. If someone is going to give up a good job with good benefits because they may have to work/live with gays, then they are not exactly making good career choices. Most civilians are for the repeal of DADT, and the younger generations are for it more in greater numbers than older generations. Those younger generations are the ones who are going to be the recruits.
Last, both young men and women join the military for many different reasons, and most people join for more than just one reason. I don't personally see how allowing gays to serve openly would take away from a guy in the military being able to feel "more manly".