In 1932, Tydie Pickett and Louise Stokes boarded a train to Los Angeles, where they were set to be the first African-American women to compete in the Olympic Games. They were in the sleeping car when one of their teammates woke them up by drenching them in a bucket of ice water. The culprit in this hostile racial assault? None other than Babe Didrikson, the golf, basketball, and track-and-field paragon who helped to bust down the barriers for women athletes. Didrikson has a heroic place in sports history, so it’s enraging and eye-opening to learn, in the new documentary “Olympic Pride, American Prejudice,” that even an athlete of her status and liberating power didn’t believe in a level playing field. The movie is about how four years later, the 1936 Olympic Games helped to sweep that attitude into the dustbin of history.