This is an issue I've given a lot of thought to over the last few years, and I think I've finally got my thoughts on it organized to the point that I can put them coherently.
There are two big items that form the core of my views on this issue. The first, appropriately, is the first amendment to the Constitution of the United States: "Congress shall make no law respecting an establishment of religion..." This is pretty clear. The second is just a simple observation. Marriage is a religious establishment. "Marriage" as a concept rises out of our religions, going back to the times when religions were the government.
Now then, taking these two ideas and placing them together, I have come to the conclusion that the word "marriage" has no place in any law, anwhere. Period. The government (in the personae of the Judiciary) should not perform marraiges. The only people that should perform marriages are religious officials. Marriage should have no relevance outside of the religious setting.
The problem comes when confronted with the question of how to preserve the benefits to both individuals and society that results from a legal union forming the core of a family unit. Marriage offers many benefits both the the participants and to society as a whole. It provides stability, a means of conserving assets, and a better environment in which to raise children.
All of these benefits could be derived from a civil union. Who a person choses to enter into a civil union with is a personal choice and should be left up to them. The law should have no say in it. If a couple who has been married by a religious official wants to have their marriage recognized as a civil union for legal purposes, then they should have the right to do that. If a couple (of whatever gender combination) wants to avoid the religious implications of marriage, but enter into a civil union for the legal benefits, then they should have the right to do that as well.
The word "marriage" should be stricken from any law on the books anywhere in the US. Let the government recognize and provide benefits for civil unions. Let the churches worry about what constitutes a marriage. If the Catholics say that marriage is between a man and a woman, they have the right to place that restriction on Catholic marriages. If individuals don't like it, they have the choice to not subscribe to that particular religion.
Now the right-wingers won't have to worry about the establishment of marriage being corrupted, and everyone can have their partnerships recognized as equal in the eyes of the law.
After extensive study, I have concluded that the Christian right is neither.