One of the more peculiar claims in today's political debate is the contention that gay marriage will undermine heterosexual marriage. I'm sorry; any logical connection between the two escapes me. I don't understand the mechanism by which one can possibly affect the other. But that's not surprising. Logic has its limitations in explaining human behavior. In this case, a lot of people are concerned about the decline of family and marriage as social institutions, and I guess it's just human nature to blame whatever seems new and threatening. In this case, gay marriage. The problem itself is very real, of...