As women were tearing off their bras in the 1960s and ’70s, George Balanchine was tearing off their tutus. You can get a full dose of the effect at the Kennedy Center Opera House this week, where the New York City Ballet is performing a series of Balanchine’s black-and-white ballets — so called because the dancers, liberated from the staid trappings of classical dance, wear little more than the tights and leotards of their daily workouts.