I'm liberal, democrat, pro-choice, pro-gay marriage, and an atheist. I could never date someone with opposite views than me.
I need someone who has the same views as me so that he wants our life to go in the same direction. I need someone who has the same beliefs as me so that I will have support for any choices that I make in life. In the past I have dated people of different religious affiliations and political affiliations and it didn't work. My choices weren't respected, and instead were viewed as 'wrong.'
In addition, I'm at the point with relationships were I'm dating for keeps. I mean the whole deal... marriage and kids. If I marry someone one who has different views than me, what would I teach my children? Would they go to church with their father on Sunday and then come home to listen to Richard Dawkins lectures with me? In the long run, dating some one with different views won't work out.