Someone asked this earlier in an online forum... (and I've corrected the poor spelling and grammar mind you.)
"I'm never going to understand how people think Chick Fil A is going to keep them from being gay. You've been gay while eating Chick Fil A before. Why does it matter what someone's opinion is?"
Well, it really doesn't... until it effects an individual's human rights via the polls. Everyone is welcome to their own opinion (no matter how intelligent or non intelligent it may be.) But when you go to the polls and vote against something that doesn't effect you personally, then it matters. When you are deliberately discriminating against a group of people and voting to keep them from equal rights in America, then it matters.
You don't support gay marriage? Fine. Don't vote for it. But why vote against it? How does it personally harm you? It doesn't. We live in a country that separates church and state and where we have religious freedom. So anti-gay marriage groups cannot expect LGBT couples who want legal, not religious recognition of their union to follow the biblical teaching.
And if you are so concerned about outlawing sin, then we need to outlaw every sin, because no one sin is bigger than another. And keep in mind, homosexual orientation (a committed relationship) is not defined as a sin in the bible if you actually read the passages in context and don't cherry-pick the scriptures.