first of all the army's purpose isn't to set standards on how homosexuals should be treated. 
That doesn't mean that they shouldnt have to follow basic human rights. It wasn't their job to let blacks into the army either, but it was the right thing to do.
second of all the majority of the men in the army are very masculine, and openly displaying your homosexualness isn't good for the whole vibe (that's not to say it's wrong to be gay in any way). 
This basically is based around the argument that all homosexuals are very girly hairdressers who talk with a lisp. The fact is that there are a wide variety of homosexual men. The majority who DO fit the stereotype are actually quite unlikely to want to join the army.
the DADT philosophy is good because it's not for or against homosexuality. As long as you don't openly do or say anything it's all good. 
It's opression of freedom of speech and a violation of human rights. If heterosexuals can discuss their sexuality, homosexuals have every right to as well
-------
They say there's a heaven for those who will wait
Some say it's better but I say it ain't
I'd rather laugh with the sinners than cry with the saints
the Sinners are much more fun...