I suppose I'm not best qualified to talk about the 'sanctity of marriage'. I have no religion whatsoever, (although some of my best Christians are friends) and I was raised in a family where religion played no part in a happy family life. When I married my first 'wife' back in the 1970's it was more for a tax refund than any concept of holy matrimony (in those days if you got married in September you received a tax refund because you were given a married man's tax allowance). No church, choirs, flowers and bridesmaids, just a couple of witnesses – one of whom I'd never seen before, nor since.
So, whilst I find it difficult to get my head around this whole marriage bit, I do support the struggle for those who wish to see same sex marriage. It isn't about being particularly in favour of marriage, it's about opposing discrimination. I just don't see why religions, especially one that is the state established church, should be allowed to opt out of discrimination legislation, whether that be employment legislation that enables them to include religious requirements for caretaker posts, preventing women becoming priests, or maintaining medieval attitudes towards homosexuality. It becomes even more ridiculous when you consider that churches are being allowed to opt out, and don't have to give their 'blessings' to any couples if they don't want to. They will be able to stick to their ancient rites and rituals enabling them to discriminate quite freely against whoever they so wish.
I suspect in a couple of decades this whole debate will be regarded as quite incredible. The views of the bigots will be seen as ancient, outdated and ridiculous, in the same way we regard those US Bible Belt churches refusing to give their God's blessing to interracial weddings.