The state's interest in marriage is protection of children and women who take time out of their lives to have and nuture children..
It is not about the endorsement of lifestiles. It is not about two people advertising to the world that "We have ageed, temporarily at least, to have monogamous sex together and will remain in the same household as long as it is convenient for both parties".
Recognition of gay marriage is just another step in the reducing the concept of marriage to absurdity.
Marriage is not a right. It is a duty. A duty for men and women to form a life long partnership to provide for their children. If it isn't that, it's nothing.