The clip I read was, indeed, offensive. But I will not be a part of any petition, online or otherwise. I have written many pieces myself deemed "offensive"; all of them have been submitted with thought and were stated as they were to express a point.
But the larger point remains. How would anyone expect a radio station that specializes in the most offensive genre of music ever produced (try LISTENING to eminem and 50 cent; though I will defend their rights as artists, they get pretty offensive in their music) expect them to "tone it down" when it comes to a subject such as this?
Put simply, I don't consider it harmless humor, but I don't think it's the same thing as dragging a black man to death in Jasper, Texas. If you don't like it, alerting others to this station's brand of *humor* and personally boycotting the station may be enough
(on the other hand, are you aware of how many folks may be drawn to the station not from the original song but from your drawing attention to it? Sometimes, the best response is silence).