Taking this further - why does government have anything to do with religion at all?
Why are there tax breaks for religions?
How does that fit in to capitalism and open markets? e.g. the Sanitarium food company in Australia, owned by the Seventh Day Adventist church. Their advertisements on TV do not advertise the fact that they are owned by the church or operate as a charity (if you're a charity why not advertise the fact!), and while as a charitable company I'm sure most of the profits go back to the community, you can certainly argue that this is state-sponsored evangelism due to the tax breaks they receive.
Why does the state have anything to do with marriage - gay or hetero?
Rather than debate about whether the government should allow or ban gay marriages, I suggest the government get out of the marriage business altogether. Marriage is about belief systems, this is personal and different people have different views. It shouldn't be legislated any more than what pants I decide to wear or what music I like to listen to - or what church I choose to belong to (if any). The government and courts should have a minimal role regarding living arrangements and tax arrangements, but only to protect people financially in case of relationship breakdowns, or to resolve custody issues.
Apart from this let people decide who they want to live with, and when, and if they are a member of a church and want to get married that's between their church, their god, and themselves.