Even if I wasn't bisexual I'd still believe that gay marriage is good.
I don't think it's the right of some to deny rights to others just because they don't like it. If you don't agree with gay marriage, don't get one, but don't deny others that choice.
With the religion thing ... I don't know if it's the same in America but just because someone declares themself as a Christian on a form doesn't mean they are one. Just saying the figures are probably a little out ...