Dan Phillips makes the point that views of marriage are necessarily down-stream from views of creation, in a very effective way:
I heard this point made recently in a sermon. Those politicians who know that "gay marriage" is an immoral and oxymoronic concept have largely talked in terms of tradition, culture and pragmatic concerns. Those have their place. But ultimately you are not coherent until you address the question "under whose authority is marriage anyway?" And that's a (shock! horror!) religious question. Until Christians are convinced in their own minds that "you're not allowed to mention religion in public discourse!" is simply a dishonest way for secularists to tilt the playing field in favour of their religion, we're going to keep missing this crucial point.