The thing is, this is not the first time something like this has happened on his show. It happens semi-regularly, although this is the first time, I believe, that Imus has done it himself; usually it is his staff.

I'd be inclined to believe that Westwood has been looking for a way to fire him for a while. While they could certainly fire him for no cause, they might be interested in avoiding a scandal on their part, and they might be trying to avoid some sort of termination clause in his contract, though that's pure speculation.