You're the only one that pointed this out, and yet Rush thanks all the time William f. Buckley and Barry Goldwater. They were the founding fathers of the new conservatives. Remember "extremism in defense of liberty is no vice." I was there when Goldwater said it.
It's probably a matter of age. For Freepers under 35, Rush may well have been their first exposure to a conservative voice with a significant audience. All we had was the print medium and, gradually, radio, until the internet became widely popular. National Review, American Spectator, and Accuracy in Media were my staples during the 70's and 80's.