...I’m 67 and have lived through some angry times: Joseph R. McCarthy’s witch hunts of the 1950s, the struggle for civil rights and the Vietnam protests in the 1960s, Watergate and its aftermath in the 1970s. But I don’t recall the degree of generalized bile that seems to have gripped the nation in recent years.

The puzzle is that many of the big issues that used to divide us, from desegregation to foreign policy, are less incendiary today. True, we disagree about guns, abortion and gay marriage, but for the most part have let the states handle these issues. So what, exactly, explains the national distemper?...

Widening inequality ... ignites what the historian Richard Hofstadter called the “paranoid style in American politics.” It animated the Know-Nothing and Anti-Masonic movements before the Civil War, the populist agitators of the Progressive Era and the John Birch Society — whose founder accused President Dwight D. Eisenhower of being a “dedicated, conscious agent of the Communist conspiracy” — in the 1950s.

Inequality is far wider now than it was then, and threatens social cohesion and trust. I don’t think Bill O’Reilly really believes I’m a Communist. He’s just channeling the nation’s bile.