The crass funnywoman was poking fun at Bieber's style on her U.S. Tv show Fashion Police on Friday (01Aug14), when she criticised the 20 year old for wearing a colourful Alexander MCQueen sweater and baggy, black leather pants with a matching leather skirt, complete with a black hat and a chunky gold chain for a trip to a Whole Foods supermarket in California.
She said, "That little b**ch just gets on my nerves", before addressing the Baby hitmaker directly, adding, "You are not a big black thug, you are just like your shoes - ordinary and completely white."
Rivers' fellow panellists, including singer/Tv personality Kelly Osbourne, laughed off the remark, but Willis claims the veteran comedienne should be taken to task for her "racist" comment.
The singer, who portrayed a traffic cop in the band, took to his Twitter and Facebook pages on Sunday (03Aug14) and shared a link to the offending clip.
In the accompanying caption, he urged fans to speak out and condemn Rivers, writing, "What Joan Rivers Said Is No Laughing Matter! It's Racist! And She Has A History Of This. Time To Shut Her Down! What Say You?"