I don't understand why the anti-gay marriage people say that gay marriage will destroy the sanctity of marriage.  While gay marriage basically isn't legal anywhere except for a few states that doesn't mean we haven't been getting "married" for decades.  We may not have a ceremony but we've been commiting our lives to our special someone.  We've been living as a married couple.  We've been raising families.  We've been paying our bills.  The thing we haven't had, that other opposite-sex married couples have, is insurance benefits, a state issued marriage license, adoption rights, hospital rights, etc.  We haven't had protection from the government.
This is where my confusion on the oppositions stance comes in.
If we've been doing all the things that makes marriage sanctified in regard to our commitment to one another and there's been no harm to the straight couples marriages, how, if we get government rights, will we destroy the sanctity of marriage?  How can the piece of paper that my marriage license would be printed on hurt or discredit another persons marriage?  How can the paperwork for the rights that we'd receive hurt them?  We already hold dear the commitment of marriage so how can a piece of paper hurt them?
I just don't understand their logic.  And I would love to hear an interviewer ask a member of the opposition this question.  I would love to hear them explain their logic.