The article to which Dan links raises questions about marriage, adoption, and child-rearing that are often found at the basis of people's concerns about gay marriage. I think there is a great deal of discomfort in US society nowadays (I'll stick to my own country) concerning these issues and, more generally, all kinds of issues relating to family. Some people feel very profoundly that the biological link between parent and child is deeply important, and the stories one so often hears of adopted children devoting large parts of their lives to seeking their birth-parents reinforces this opinion. (So-called open adoption bypasses that problem.)

I think one can understand why someone with strong enough views along these lines would be opposed to gay marriage, in so far as gay marriage would instill certain kinds of parental rights. Of course, as has often been pointed out, such rights existed in Massachusetts before gay marriage was recognized, and there are many other jurisdictions in which such rights already exist, as well. Moreover, as the writer of the article to which Dan posted noted, such concerns do not seem to have a great deal to do with gay marriage but with deeper questions about adoption and child-rearing. Nonetheless, such concerns do tend to surface here. And, while one may find such concerns misdirected and unconvincing, they aren't necessarily bigoted.