"You can't be a Conservative and a Comedian" - What does this even mean?

Quite frankly, much of Rush Limbaugh’s appeal in his early days was that he was very funny. Eventually (somewhere around the Clinton impeachment era) he became a more humorless political commentator, but before that, he was genuinely funny and obviously conservative. His fake advertisements hold up well against those of SNL, and his song parodies were laugh-worthy as well.