In the 2005 movie, “Crash,” writer-director Paul Haggis sets up a series of scenes designed to tease out the snap judgements we all tend to make upon first encounters with new people: the redneck-sounding white cop, the black youths lingering on the street, the Mexican locksmith making a house call—all caused kneejerk, “protective” reactions among members of a different race or class. By the end of the film, however, our impressions of all but one of the characters changes 180 degrees.