Malky McCormick ranted at Nicola McCormick in front of shocked neighbours after battering his victim's door with a crutch before waving it in the air and calling her a "b******".
McCormick, 69, then turned to astonished witnesses in the normally peaceful community and told them to "get to f***".
McCormick, one of Scotland's best-known cartoonists and illustrators, was fined £350 after admitting breach of the peace in a case described as outrageous by Sheriff Alistair Watson. He was cleared of assault.
The incident in Fenwick, Ayrshire, happened after McCormick's daughter-in law put his son Dominic's clothes in bin bags after they fell out.
Mrs McCormick, 36, said her father-in-law hit her with the crutch and seized her by the throat.
McCormick told Kilmarnock Sheriff Court he was "ashamed" about causing the disturbance in July 2011, but denied assault.
Sheriff Watson convicted McCormick of breach of the peace but said the alleged assault was "firmly on not proven territory".