Down through the ages, homosexuality within military organizations has been used variously for breaking up military discipline, integrating an intense loyalty in a unit, a cause of hazing the unfortunate individual who made the mistake of exhibiting borderline behavior, and celebrated as a "great liberation".
The Democrats, very few of whom have served on active duty, tend to celebrate overt homosexuality as some kind of liberation, but with the intention of breaking up the effectiveness of military discipline. Same reason they tried to force the Boy Scouts to accept openly gay Scoutmasters. It's all about extending the agenda.
I always thought that the reason to bar gays from the military was to keep sexuality out of the units. When I see the way that women in the units have sexualized operations (particularly Abu Ghraib, but also the number of pregnancies on ships), I think that argument is long gone.
If we can mix heterosexual men and women, why not homosexuals?