As cities across the country honored Jackie Robinson's pioneering baseball career, one also apologized for its racist treatment of Major League Baseball's first black player nearly 70 years ago. When Robinson's Brooklyn Dodgers played the Philadelphia Phillies in 1947, he was told to ''go back to the cotton fields'' by the Phillies' manager, refused service at a local hotel and taunted by players with racial slurs when he came to bat. On Friday, Philadelphia's city council publicly acknowledged the incident as a dark chapter in the city's history.