Coming from someone who grew up watching dangerous amounts of television, I do remember several instances of use of the "N-word" in Norman Lear sitcoms.
ALL IN THE FAMILY:
1) [Lionel Jefferson's Engagement Party episode] The Bunkers/Stivics are invited to Lionel's engagement party where George Jefferson learns for the first time that fiancee Jenny Willis's father is white. George complains to Louise "Ten more seconds he'll be calling her [Negro]." Archie overhears this and remarks "Listen to that. I ain't used that word in three years."
-- circa 0:07:05 in.
2) [Archie and Mike locked in the Archie's tavern’s storeroom] Archie opens up to Meathead and relates a schoolyard story in which he was beaten up by a black classmate for having called him a "[Negro]." [IMHO, this was the last GREAT episode of "All in the Family”].
-- circa 0:01:20 in.
SANFORD AND SONN
1) [episode where Fred is in court fighting a traffic ticket] Fred uses the objectionable word twice when he comments about the lack of Caucasians in traffic court to the arresting officer with "Look at all these [Negroes] in here" and "Look around here. There's enough [Negroes] in here to make a 'Tarzan' movie!"
-- circa 0:00:40 in.
2) [YouTube clip; party scene. Episode?] Fred directs some mock cheers towards Rollo; "Bim! Bam! Boom! Somebody get this {Negro] out of my room!"
-- circa 0:00:29 in.
THE JEFFERSONS:
1) [episode?] Moses Gunn portrays a friend of Lionel's who seems to be shaking George down for some sort of pay-out. When George retaliates, Gunn's character rejoinders with "What's the matter with you, [Negro]?" and "You're crazy, [Negro]!"
-- circa 0:01:25 in.
2) [episode?] George and Weezy are entertaining a snooty upper-class black couple connected to the Social Register, and when the visiting gentleman insults maid Florence, George defends her with "[Negro], what the hell did you say?”
– circa 0:00:47 in.
3) [George vs. the KKK; objectionable usage scene unavailable via YouTube] Through a series of miscommunications coinciding with reports of graffiti/vandalism in their building, George, Tom, and Bentley, attend a meeting for a group desiring to “clean up” the building unaware that it is actually a KKK meeting led by James Karen (the nice guy from the Pathmark supermarket TV ads). At one point, Karen’s son (Ike Eisenman from the Disney “Witch Mountain” movies) calls George the N-word. The notorious pay-off during the fracas results in James Karen suffering a heart attack, George administering CPR to the unconscious Karen, and Eisenman informing Karen that George saved his life. As James Karen is being wheeled away by paramedics, he tells his son “You should have let me die.”
GOOD TIMES:
This programme usually euphemized the N-word with “Negro.” However, there are several times where Wilona wants to say it but the scriptwriters had already applied this neutralization. For example, in the story arc which introduced Janet Jackson’s “Penny” character [unavailable via YouTube], Wilona brings abused child Penny to an emergency room after Penny’s mother had broken Penny’s arm. Since Wilona is not Penny’s legal guardian, the attending emergency room doctor refuses treatment, prompting Wilona to get in the doctor’s face with something to the effect of “Negro! There’s an abused child here!”