If this report is accurate, then an argument being made against gay marriage by the Keep Marriage Special campaign is as laughably bad as others on the same topic which I have featured on this blog. The argument in question is the following:
If the only basis for marriage is the desire of the parties to get married then there is, according to the logic of this proposal, no reason not to open up marriage to more than just same-sex couples. Polygamy, polyandry and incest would all be permissible.
It's laughably bad because it is of the form...
If the only basis for eating is being hungry, then there is, according to the logic of this thesis, no reason not to swallow steel nails or ingest poison.
Generalizing, the KMS argument picks out one relevant part of the case for gay marriage, ignores another - crucial - part, and constructs its oppositional case in that pathetic way.
For those in favour of gay marriage, the desire of the parties to get married is not the only basis of their view; this also includes the assumption that gay marriage won't significantly harm anyone. Opposition to polygamy, polyandry and incest, they might well hold, would. The response of Ethan Bourne - namely, that 'What the Keep Marriage Special campaign is doing is talking about a different issue altogether' - is fair enough, but it doesn't really expose the misstatement of the case for same-sex marriage that KMS permits itself in order to oppose it.