"born gay": wrong. proof: athens, sparta. treat women like dirt and you get dirty women and men who prefer something else
"gay marriage": you don't like gays? get rid of your democracy, same proof, athens and sparta. Personally, I'd dump "true believers in the literal word" before gays, since the Bible treats women like dirt.
"crypto-statism" : I say the government can't walk into Church and tell the Preacher who, before them, can marry.
"bio-messiness": XXY, hermaphrodites, those who change by of their own volition, the government can't walk into Your Body and tell you what gender you are, and therefore, who you can marry.
"polygamy": I think legislation distinguishing gay marriage and polygyny/polyandry is trivial, and the slippery slope people are grasping at straws. The government might not be able to really tell what gender you are, nor whom the Church can marry, but the a Government (although I wouldn't make it the Federal) could easily say "two people, max" (and through the tax code, they already do).
"bestiality & children": canard. neither has legal will, so can't enter a contract in any event