Yes, imus shouldn't have said it and yes, it was offensive. I don't think it was racist, although what his co-host Bernard said, was.
As for sharpton, the man who is the leader of the free world should be above whining about a phrase from a stoner radio host to anyone who would listen.
Imagine Reagan calling up everyone he knew, telling them how offended he was that some lame radio host said something mean about someone. I mean, perhaps he (Sharpton) just wants the press... but with his name and experience, I believe he could achieve that same platform by doing something great to change lives - not crying about words.
I just don't see Sharpton being able to go from "he said this, i'm telling everyone how upset I am" to sitting down with lifetime hardballers from Russia and China and Iran and showing, well, dignity and confidence.