It was probably because he believed the joke and couldn't see it as ironic or funny.
Hell, now that I think about it. He never laughed at any of the racist jokes I made about black people and Mexicans.
Expanding on the point Vimana made, tryign to tell a racist joke about blacks around an actual racist would go something like this:
Me: "Why can blacks run so fast?"
Racist: "That's a fuckin myth, naygers ain't special"
Me:"It's a joke man, Why can blacks run so fast?"
Racist:"Uh, cause they are closer to monkeys?"
Me: "Cause they get so much practice running from the police!"
Racist: "Damn right they do!! Damn naygers always stealin shit and killin people!!!"
etc.
The crime thing is not a myth. Black on black and black on white crime is much higher than white on white or white on black.
Onder wins. Was wondering how long it was going to take for someone to say "Derpyn". But when you get tired of being a societal parasite Onder, you can have a legitimate beef with the gypsies or whatever.
Probably because of poverty. White criminals are disproportionally poor, and blacks are generally poor. I'm not saying that poverty directly causes crime, but it is a strong contributing factor.