The only possible reason I see that would advocate DADT is if the advocating of homosexuality would cause a rift in military morale and effect our fighting forces thus effecting our national security.
Twenty years ago, maybe. What with all the homophobic bravado conditioned into our fighting forces. But today, not so. Our youth making up the majority of the armed forces have different, more tolerant, attitudes these days. I don't think doing away with DADT will bother them that much.
These days, practicaly everybody knows a gay person they respect and like. It's not like it used to be. Our youth today are MUCH smarter than the youth in previous generations and far more tolerable.
Who would you rather have working with you? A gay person or a red-neck homophobe? And there you have it.