I genuinely don't want to rag on religious people, but I don't think that's legit. "We need to cut out peoples' hearts and offer them to the gods, because if we don't the sun won't rise" is not a "rational" argument for human sacrifice by any useful standard. No more so is "we need to deny gay people human rights because God wants us to." No amount of earnest belief makes that argument remotely valid.

So, no, there are zero rational reasons to oppose gay marriage, only irrational, bigoted reasons.