You think that married gay couples"degrade the moral fabric of our society" more than unmarried gay couples?I understand your argument but it still does not make sense as to why we should legalize behaviors that will degrade the moral fabric of our society even more.
Personally, compassion factors highly in what I consider to be "the moral fabric of society"; for instance, I would not want someone's child to suffer because of my personal stance on morality. I guess views on that vary.