Isn't focusing on religion a bit of a strawman anyway? Opposition to gay marriage also has its roots in human survival and biology. Hetero relationships are necessary to prevent human extinction. Natural selection favors hetero couples to keep the human race going.
If 100% of marital couples were gay, the human race would go extinct in a couple of generations. Hetero marriage contributes to the common good whereas gay marriage is detrimental to the common good.
That's overstating things a bit don't you think? What you're talking about will never happen because there will always be more straight couples than gay ones. The whole procreation argument has never made sense to me.
