once i was watching a commercial about an airline. in it, a black guy wore so much clothing before he left on a trip that he looked like the michelin man. he did that so he wouldn't pay any charges for luggage. if he had flown on the airline in the commercial, he wouldn't have been charged for luggage.
i laughed at the situation, but quickly wondered: is this commercial bigoted?
i decided it wasn't. here's how i determined that. you could've put a white guy, an asian or a hispanic in the same situation and it still would've been funny.
so if any minority is in a silly/foolish/stupid/ridiculous situation, and you substitute a different person in it, you're laughing at a human foible. that's appropriate.
but if you don't get those laughs with the substitution -- then it's bigoted.