Navajo Nation -- 'Mike & Molly' Joke Is RACIST!!!

The Navajo Nation is LIVID after a joke aired on "Mike & Molly" ... calling Native Americans a bunch of drunks ... and now the group is demanding an apology from CBS.

In case you missed it, Mike's mother on the show -- an Archie Bunker type -- says, "You ever been to Arizona? It's just furnace full of drunk Indians."

The joke isn't sitting well in the Native American community. A rep for the Navajo Nation tells TMZ, "For a show like this displaying us in a negative light is just unacceptable, they are taking a shot at the entire state of Arizona and its indigenous people."

The rep says, "An apology would be the right thing to do, but some damage done can't be fixed in an apology."

Calls to CBS weren't returned.