THIRTEEN years ago, Vice President Dan Quayle attacked the TV sitcom “Murphy Brown” for the title character’s bearing a child out of wedlock, claiming the show’s failure to defend traditional family values was encouraging America’s youth to abandon marriage. His speech kicked off more than a decade of outcries against the “collapse of the family.” Today, such attacks have given way to a kinder, gentler campaign to promote marriage, with billboards declaring that “Marriage Works” and books making “the case for marriage.” These campaigns share the idea that people are willfully refusing to recognize the value of traditional families, and...