Ivan Dixon, who died this week, is best known for appearing on “Hogan’s Heroes.” But I believe he will be best remembered for his pioneering work as one of the first African-American directors and for his work on behalf of diversity in show business on both sides of the camera. Everyone should see his film “Nothing But a Man,” a brilliant but little-seen 1964 film that frankly explored the pressures and challenges faced by a black man in that pre-Civil Rights Act era. It has a quiet, documentary feel and a brilliant Motown soundtrack but the anchor is Dixon’s performance as a man whose pride cannot be diminished by the constant attempts to erode it. Dixon’s co-star is the lovely jazz singer Abbey Lincoln.