Also, I'm going to double post and call back to the comment made earlier about how people can't take a joke. There's actually a scientific theory about that. The [url=http://leeds-faculty.colorado.edu/mcgrawp/Benign_Violation_Theory.html]benign violation theory[/url] states that in order for a joke to be considered funny it has to violate a perceived norm while being benign in nature. But when a joke actively or is told in a threatening way to an individual and it violates the benign aspect of the joke, then it becomes threatening.

There's a correlation with the punch up/kick down rule too. Commonly, jokes that attack upwards (against political leaders, business executives, celebrities, etc.) are considered OK because the people they attack are considered out of harms way or can recover from the criticism. Where-as kicking down in considered in poor taste because it already damages people who aren't in any shape to take it.

You could translate this into the complained scenario earlier that people can't take a joke because the joke is a fundamentally racist one into this: it's in poor taste for a white person to tell a joke about black people to a black person because it's a kickdown in most cases on the basis that blacks in the US have historically had the shit-end of the stick like Native Americans. They's so far down on the ladder that it's just evil to kick them down when the other group is so high up.