What bobblehead said is the crux of the matter. Believe it or not, there are still people that believe in the whole sacred union part of marriage - that it's not just a civil service or a joining of health care benefits, but a religious vow. Those people want to protect that definition for themselves more than they want to stop a couple of queers from wearing matching wedding dresses, holding hands, and being recognized as a joined couple. They can call it whatever they want, but it's not marriage.