If it's a racist "joke" then by definition it is not really racist. It's just making a joke about something related to race. If you made a racist joke, but you didn't intend it as a joke, then your just rude, but I've never met anyone who has done that.
(Online I talked to a guy who was black who said that black people are the superior race because they can't be racist. I facepalmed so hard, but then realized he was serious. That's the most racist thing I've ever heard anyone say.)