I didn't spot this thread til after I posted in the other newer thread.
Polygamy was ok in the bible, as were underage marraiges. A whole gamut of situations are chronicled in the OT. That's not the point though, this debate is about how society has moved morally. People in general have put aside their bigotry against gays and have decided that they deserve equal rights. Why shouldn't it extend to marraige?
Looking at the legal arguement, in addition to all the other inconsistencies you had laws banning mixed race marraiges not so long ago. Are you really trying to say that because it was on the law books that it was right? The legal definition of marraige was one man and one woman - so long as they were the same colour, that has changed so why shouldn't it change to include same sex partners. We are not talking about legalising beastiality or paedophilia but about affording gay people equal rights under law - one nation indivisable and all that malarky.