Because no one who has shown up in this topic as of yet wants to argue against allowing gay marriage. But here are some quick arguments I suppose:
1. God says gay marriage is wrong. Therefore it is wrong. Wrong things should be illegal. Therefore gay marriage should be illegal.
2. The purpose of marriage is to produce children. Gay marriage does not produce children. Gay marriage does not achieve the purpose of marriage. Therefore gay marriage is not marriage. Therefore the state should not call gay marriage marriage.
3. Marriage has always been understood to be heterosexual. Therefore the definition of the word marriage involves 2 people of different sexes. Therefore a gay marriage is not a marriage by definition. Therefore it is silly for the state to try to define gay marriage as something it is obviously not, just like defining red as blue by fiat.
You can disagree with any of these arguments, or any of the other arguments against gay marriage, of course. None of them offers conclusive proof.
Your biggest problem with these 3 arguments at least is the basic premise. Does God really think gay marriage is wrong? Well, whether he does or not, that's not an issue with the argument anymore, but with the underlying facts. The argument can be reasonable even if the underlying facts can't be shown to be correct, or even if they are wrong.
--
Congratulations to SuperNiceDog, Guru Winner, who was smart enough to pick
your 7 time champion, Link.