Remember when Michael stopped believing in God? Oh, man! That was a very important episode.
Both Esther Rolle and John Amos wanted the JJ character written out of the show. All the other characters were somewhat serious and had depth, but not that one. They wanted to use the show as a vehicle for social change in the black community (that's why the family had both a mother and a father), the producers simply wanted a sitcom--JJ was the show's money-maker. Eventually, they both left show.