Many people get kicked out because somebody finds out that they are gay, not because that person has declared their sexuality while enlisted in the army. And even so, it is discriminatory to deny somebodies right to declare their sexuality. Why should a gay man or woman have to either make up stories about a girlfriend/wife back home or not participate in conversations revolving around that just so they wont get kicked out of their position? You probably dont understand because (assumption) you are straight, but pay attention to how often you make your sexual preferences known during the day. Making people not be able to tell about something as simple and basic as a partner (whether it be male or female) is downright disgusting. Imagine not being able to talk about your sexual preferences without the imminent risk of being fired or sent home...
And the argument that DADT removes relationships from forming on the field doesnt hold because WOMEN can also fight in battle. Using that logic, women should be excluded from field combat (which I do not agree with). Also, the argument about DADT increasing group cohesion is also null because if you are willing to join the army, why would you not try and make the group work, especially when it dictates whether or not you live or die? Both of these arguments, as well as many of the others supporting DADT, are ridiculous.
Of course, coming from a gay man, my post is definitely biased, but DADT is a blatant human rights violation no matter how you look at it.