I heard/read somewhere that the clintonistas are behind this. I do remember that he badmouthed the toon at a dinner one time.
Imus supported(confusingly so) McCain, Harold Ford(who ditched him after the I-man got death threats for his support of Ford)and John Kerry but openly hated Hillary.You really could have something there.
The Soros funded Clintonista organization, Media Matters, started the ball rolling. They have full time paid staffers who monitor each show, concentrating on conservatives like Rush, but also including others who are of less conservative bent like Imus. The WSJ has a very good summary of the events in the Imus affair.
Media Matters is headed by David Brock and was set up and is still largely funded using Soros money. It was created with the help of Clintonista John Podesta. David Horowitz excellent web site Discover The Networks, has great break downs on Brock, Podesta and Media Matters. Follow some of the other links on those pages as well. They are fascinating.
And, yes, it is very believable that the rest of the actions summarized in the WSJ were also orchestrated, or at least "encouraged," by the Clintons