I'm all for getting religion out of the government. And as for people who argue it's a religious thing, I'm Pagan, and see nothing wrong with same sex marriage. So why can't Pagans have a legal same sex handfasting? It would be a religious ceremony sanctified by whatever gods the couple believed in. I'll tell you why. Christians believe that they're the only ones that matter. They don't want any other religion to have a say. They think they're Bible is absolute law and the whole world must follow it.
Though let me make myself clear. I don't dislike all Christian people. I like open minded Christians just fine. It's the biggoted, Bible thumping, closed minded blow hards that use their God liked a club to beat people over the head with that I think need to be taken out to a field and shot. In other words... extremists.
Regardless, marriage has been made into a legal contract. If I were to be married to a woman, and gods forbid something happened to me, my wife would be next of kin. She would speak for me. If we had kids and I died the kids would be hers. A house, a car, pretty much anything I owned she would have claim to.
Same situation, but with my boyfriend. Some progress has been made I know, but if I died he's screwed. My mother could easily come in and take everything, leaving him with nothing. If we had kids and they were mine, they could be taken from him.
Tax laws, property laws, parental rights, all government things, and all affected by marriage. If you want a divorce, you don't go through the church, you have to hire lawyers and sign legal documents. What each spouse is entitled to is written into state law. Hell, you don't even have to be a religious official to perform a legal ceremony. One of my cousins was married by the captain of a cruise ship. It's very much a legal, government recognized thing. If Christians feel it is against God, then they can remain heterosexuals. Those who don't believe in their God have just as much right to have all the same benefits.