Seems to me like a lot of humor depends to some degree on the misfortune of others. In the case of the "dumb _____" genre, it'd be the misfortune of being ignorant/uneducated, I'd guess.

In the example you posted, race was pretty clearly implied by the antebellum Ebonic dialog, like "Lord chile". Names, too, like "Rastus"...but then, in my series, names like "Bubba" are pretty clearly associated with white people. It was subtler, but maybe Tom's perception that the jokes were describing white folk has some truth to it after all.

In both sets of examples, the dialog itself was a large part of what made it funny. That kind of schtick seems to upset people less than jokes directed at some other characteristic of a group. I don't think anybody objects when Mel Brooks (a Jew) turns on the "oy vey! gefiltefish!" patter*, where other Jewish stereotypes can really make people go ballistic.

Nomsayin?

Oy vey! I'm not sure what I'm saying, actually, just random thoughts on humor. It's too subjective to pin down with rules...I know it when I hear it, I guess.

--Robert

*--"Spaceballs" was two hours of Jewish jokes...and one of the funniest movies ever made. "She's a Druish princess? Funny, she doesn't look Druish" [snort]