Around the same time, a New York University psychologist, Jonathan Haidt, was formulating a theory about why liberals and conservatives have such a hard time productively conversing.
After mucking around in a lot of survey data, he came up with this basic idea: Liberals and people of the left underpin their politics with moral concerns about harm and fairness; they are driven by the imperative to help the vulnerable and see justice done. Conservatives and people of the right value these things as well but have several additional moral touchstones — loyalty, respect and sanctity. They value in-group solidarity, deference to authority, and the protection of purity in mind and body. To liberals, those sincerely held values can look a lot like, in Dr. Haidt’s words, “xenophobia, authoritarianism and Puritanism.” This asymmetry is the fountainhead of mutual incomprehension and disdain.