Quite frankly, I'm not surprised at all. And really, I don't find the "parody" itself any more offending than the countless "parodies" of, say, President Bush. Granted, many of those are nearly as hateful in their deep-seeded bigotry and furtherment of geographical stereotype.
And while it's a horrible thing, there is little that can be done about it. Rush, in this era of XM Radio / Sirius, and all these new systems allowing us such a variety, has been pitted to nothing more than one of countless shock jocks. He's just more unsightly (than most), most influential (in a "seeding-further-ignorance" sort of way), and annoying.