Gay Marriage

"Homosexuals
should be able to marry."
How's this in question?

I can understand how someone would be against abortion. I can understand how someone would be against universal healthcare. I can understand how someone would be against gun control. I can understand how someone would be against affirmative action.

But I can NOT, for the life of me, understand how someone would be against homosexuals being able to marry... What logical argument is there...? Anyone...?

Making history... Obama Backs Gay Marriage