He did not make fun of Fox. In fact, he's gone out of his way to disabuse himself of that notion.
He has said that he was trying to describe what He was seeing as he watched Mr. Fox. I've actually done a little radio in my time and I used to laugh at myself for gesturing, and then I would worry if I had relied too much on my gestures and not let my words paint the picture.
Consider a minute: Do you think Rush would do something as reprehensible as "mock the afflicted" right out there where anyone could see? Even if we stipulate, for the sake of argument, that he is a cynical and evil man, we have to grant a certain native cunning. SO it is hard to think he would do something at once so stupid and so vicious.
But, on the other hand, the MSM have already shown themselves all too eager to believe on the flimsiest evidence the worst of those down upon whom they look. SO it's not surprising that they would characterize this as mockery. It is surprising that you would -- that anyone would -- trust their judgement.