What do you find offensive about the sitcoms?
They overflowed with gross stereotypes that did not advance black characterization forward. Producers such as Norman Lear thought he was some "king of relevant TV," but he--and the writers/producers of other series--added stereotyped characters that were--in some cases--as bad as the kind of crap seen in the
Amos 'n' Andy (the TV version), or the human joke characters in Golden Age Hollywood short subjects (e.g. Dudley Dickerson's work) that only existed to scream, bug their eyes and issue an encyclopedia's worth of offensive behavior and/or catchphrases.
Good Times' John Amos left the series (fired) in large part due to his heated criticism of the intensifying, black modern-day minstrel / assclown antics of Jimmie Walker's J.J. character. During its development, Amos was led to believe (by Lear) the series would take a more serious look at a struggling black family, but as the J.J. antics proved popular (
so much can be said about that), the PTB wanted to play both J.J.'s act and catchphrases for all it was worth. Amos' departure had nothing to do with network-fed stories of the actor wanting to move into serious roles.
Additionally, a significant motivator for Bill Cosby to create
The Cosby Show (in the following decade) was to stand as a full-on fight against the kind of 70's black sitcoms that sold a generation of audiences on the idea that African Americans were sideshows--subject to racial mockery.
As noted yesterday, there was an explosion of black performers cast in TV, but
drama was where the real advances were made (much like 1960s American TV), with only a couple of characters on other sitcoms not falling into that sideshow / minstrel category.