IT’S NOT ABOUT MARTIN LUTHER KING, but this civil rights holiday is still a good time to plug the under-appreciated Separate But Equal, a movie about the Brown case starring Sidney Poitier as Thurgood Marshall. When it came out, my old lawprof Charlie Black, who’s portrayed in the film, told me “They got Sydney Poitier to play Thurgood, and then they found some SOB who looked just like me to play me.” That was kind of unfair.