Explain this Greg Bear radio segment please?

I’m a little confused by this piece by the author Greg Bear about Rush Limbaugh. As far as I understand it he’s satirising the radio announcer by joking that he couldn’t actually be for real.

In my defence I’m not American and I’m only aware of Limbaugh himself through cultural osmosis.

Link below, I think its OK but as always clickers beware.

http://whatcanimake.noip.me:8000/mike/secdir/books/scifi/unsorted/Ebooks%20-%20Over%20300%20Authors%20-%20Science%20Fiction,%20Classic%20Fiction/Fiction/Greg%20Bear/Greg%20Bear%20-%20Rush.htm

Yes, you read it correctly. You might be hindered by the fact that it’s not particularly funny, and I say that not even liking Limbaugh.

This was written in 1994. Science fiction writers are the worst at predicting the future.