Any excuse for the Soros left to try and silence Rush, conservative thought, and free speech. Limbaugh will be a much more difficult target for them than the lib Imus.
I suspect Rush is essentially throwing down the gauntlet to the liberals, challenging them to take him down. He is the 800 pound gorilla of conservative talk radio: no one, not Hannity, O'Reilly, Savage, Levin, or anyone else you can name, has half his impact. Except for O'Reilly, none are particularly vulnerable to a national boycott because most of the sponsors are local businesses in the hundreds of markets they serve. The businesses sell mostly to white males, who would ignore any call by Jesse Jackson or Al Sharpton to boycott any given conservative talk show.
Rush knows this, and, in all likelihood, Jackson, Sharpton, George Soros, etc., know it too. So good for him in taunting them with the "Magic Negro" ditty.