Gay marriage right or wrong:
This idea is essentially playing with semantics. Most people who are against gay marriages are really against gays, so calling it a "civil union" might shut their mouth, but will still not satisfy them. Furthermore, the effects on society are bound to be minimal on an overpopulated Earth where global warming will drastically reduce the already overtaxed ability of Nature to feed us.
And if "undermining the assumptions of law that has developed over hundreds of years" is really an issue, than law should never change. We should revert back to tribes & slavery - why challenge any assumption?