Ezra Klein is a columnist at the Washington Post, as well as a contributor to MSNBCThe season premiere of “Mad Men” ended with Don Draper staring at the front page of the New York Times from Jan. 1, 1968. “World Bids Adieu to a Violent Year,” reads the headline. (The Times story, by Murray Schumach, is real; you can read it here.)As in “Mad Men,” a sense of dread pervades the article. “Nations said farewell to a year of violence, tension, and economic uncertainty,” it reminds readers, who will soon discover that the new year brings even more lurid violence than the one just past. The accompanying photograph shows two people, backs to the camera, umbrellas open against a snowstorm, walking through a deserted Central Park. It’s bleak.