Actually there were plenty of Biblical arguments bandied about by anti-miscegenationists and one of the judges in Loving v Virginia even said that God separated the races and so it was against his will for people of those races to unite themselves in marriage.
Plus not all Churches are against gay marriage. Quakers, Unitarians and Liberal and Reform Jews are all in favour and want the right to perform gay marriage ceremonies. The Church of England is also incredibly divided on the issue with even some bishops calling for the Church to allow same sex couples to marry. The Lutherans in Denmark and Sweden already marry gay couples. So it's not all that clear cut really.
Oop I should do more research
sorry! I wad raised to believe the only reason people disliked inter racial marriages was because of racism (well that's what we saw in our family against my uncle). The Church is deeply divided in general about it. I agree with what you said above...I won't have a gay marriage either. I prefer the term equal marriage. Putting sexuality in there imo is asking for a violent conversation.