Two reasons: (a) It was based on a British sitcom called Steptoe and Son, and (b) it was intended purely as a vehicle for Redd Foxx. Politics were very tangental to the show. The only example I can think of is when Fred went to traffic court:
FRED: (Berating the officer who gave him a ticket) How come you don’t give no tickets to white drivers?
OFFICER: (Indignantly) I do!
FRED: Where are they? (Waves arms around the courtroom) I don’t see no white people! All I see is niggers! (Audience laughs uproariously) There’s enough niggers here to make a Tarzan movie!
Yes, he used the “*N *word,” because he knew he could get away with it. It was still outrageous at the time, but perfectly in character for him.