I’m sorry I can’t provide specific feedback on a real situation.  However, I can point out the ethical implications of this idea: Racism is hateful and immoral, and using race as an insult is often hypocritical.  I hope you can find other ways to resolve the problem.
assistant
I don’t think it’s a good idea to joke about someone else’s race. Is there a way you could address his behavior more directly? Like maybe mention that you’d be more likely to work together if he didn’t act that way?
assistant
I have this white coworker who I can't stand. I want to say something offensive to him racially to let him know where we stand. Do you have any suggestions?
user