I am not sure about the various arguments that have been put forward by traditionalists as to why homosexual sex and marriage is bad for society.
On Prime Time, Susan Philips argued that the introduction of gay marriage would undermine her heterosexual marriage. I am not sure. What other people call their relationship won't radically change what I have with Caroline.
Christian author Joe Dallas believes that any acceptance of gay relationships will eventually lead to the exceptance of pedophilia. But I am not sure that the slippery slope argument is a strong one.
John Stott (in 'Issues facing Christians today') and Thomas Schmidt (in 'Straight and narrow') point to the evidence that homosexual relationships are inherently unstable. There may be truth in this, but at least some same-sex relationships survive over the long term. I am sure that there are many who will simply respond to this line of reasoning by pointing to the many unstable heterosexual relationships.
The Iona Institute put the emphasis on the role of children and adoption. I do think that the rights of children often seem secondary in this discussion. I also believe that the ideal for any child is to have a loving father and mother, who love each other. The Iona Institute argues that there is a difference between circumstances which mean this ideal is not met (e.g. when one parent dies) and intentionally designing situations in which this ideal is not met (e.g. legalising adoption for gay couples). But someone may argue that they simply want to marry their same-sex partner and that they have no desire for children.
I believe in the separation of church and state; I do not believe any nation is in a covenant relationship with God (as Israel was in Old Testament times); nevertheless, I do believe that the Biblical teaching on sexuality has a relavence for the whole of society. I believe that nations are accountable to God and I don't believe that we have the right to reinterpret the God-given institution of marriage. I also believe that God gives his commands for the good of people, and while I may not understand why, it would seem that gay sex and gay marriage are not in people's best interests.