It has been a while since I read the galleys, and a friend has borrowed my copy of the book, so perhaps D&S address this objection in the book and I have simply forgotten it (or perhaps the book has been modified in pertinent respects since I read it). But from what I can recall, Matthew Continetti accurately summarizes a portion of their argument in his review:
[D&S] argue it is entirely rational for working-class voters to cast ballots on social and cultural concerns. That’s because issues “from abortion and marriage law to the death penalty and immigration” are “at the root of working-class insecurity.” They reverse the left’s chain of causation. Whereas the left says social pathologies result from economic immiseration, Douthat and Salam say that economic anxiety increases in direct proportion to social instability. . . .
The social disruptions of the last 40 years–rising levels of divorce, illegitimacy, drug use, and crime–have hit voters without college degrees the hardest. Those disruptions prevent the formation of stable families. And without stable families, people lack both a refuge from and a mechanism by which to cope with larger structural changes in the global economy.
This explanation for the relative social conservatism of working-class voters seems persuasive only at a high level of abstraction. First of all, is it in fact true that these voters are more likely than other voters to object to cohabitation, divorce, or illegitimacy? (I’m talking here about their views rather than their behavior.) And what do the issues where they do seem to differ from voters higher on the income scale–such as same-sex marriage and abortion–have to do with their economic conditions?