Don't believe in gay marriage? Don't have one. That is your right.
My religion prohibits me, as a rabbi, from officiating at interfaith marriages. That is my religious right. But I would be *outraged* were the law to prohibit me from doing so. That should be my right as an American.
I don't impose my religion on other people and I don't want them imposing theirs on me. And I most certainly don't want the government telling me what I can and cannot do regarding religious matters.