The same arguments used against gay marriage are the same arguments used back in the day against interracial marriage.
Here's my opinion. The need to remove the word marriage altogether. Make everything a civil union, and if you want to be "married", talk to a priest of some sort. Basically, take this argument out of the government. Nothing would change, except all the people that, for some reason, have a problem with Gays using the term "marriage", would be placated. It is all semantics, and therefore stupid IMO.
How I really feel, is that this is a simple case of ignorance. People are bigoted due to their ignorance and are told to defend "marriage" tooth and nail. It doesn't matter if two gay guys get married. It doesn't affect anyone besides the two getting married. People need to live their own lives to the best of their abilities and stop trying to tell everyone else how to live theirs. Stop the bigotry and hate. It is unnecessary and will shorten your lifespan.