The selection of J.D. Vance on Monday as Donald Trump’s running mate is a direct result of the political media’s failure to understand class in America. For his 2016 memoir, “Hillbilly Elegy,” Vance was venerated by many journalists and book critics as a powerful voice representing long-overlooked Americans. But he’s no working-class hero.Vance portrayed this group — 35% of Americans, by the way — as tragic victims of alcoholism, drug abuse, laziness and their own self-destructive moral failings. Journalists ran with that, bringing their own stereotypes to depict the working class as angry, uneducated white men driven by economic insecurity...