I have seen a lot of things from people who say they want to "protect marriage" by barring homosexual marriage. Seriously, I cannot make out what they perceive as a threat. Your wife is not going to leave you because two men in love can have their union recognized by the government. If your wife leaves you, it will be for other reasons.
Now, I have no interest in protecting marriage at all. It is a religious institution. And the government should not be giving special privileges to married couples. The only reason gay marriage is an issue is that people want equal rights. (What a concept.)