Despite their surface plausibility, none of these arguments withstand more than cursory scrutiny. Consider the case of the radio personality: of course nobody had ever successfully argued on his show that two men or two women marrying each other would harm their own marriage, because nobody anywhere defends traditional marriage on that ground; the arguments against redefining marriage are much more fundamental. The real question is whether then union of a man and women is different from that of two men or two women (hint: the answer has something to do with babies), and whether the state has an interest in fostering and protecting exclusive heterosexual relationships that it does not have in same-sex relationships. The radio host didn't mention whether he had ever had that discussion on his show (curious, because that is what I hear defenders of traditional marriage talking about).