Why are people so against the "Don't Ask, don't tell" repeal?

And also, let me ask about gay marriage while I'm at it. I am a democrat but I really do try to understand both sides. I don't just watch 1 news station, or read one paper. I really try to understand both points of view, and for some things, I do. And some things, i cannot wrap my head around....this being one of them. Gay people are people.Shouldn't they be treated just like everyone else? Don't they deserve to marry the one they love? Or join the military and be open about their uality?