Hardly qualifies him as an "idiot," I'd say.
Seems to me Rush merely used the lesser of two possible comparisons which made the comparison more palatable for most people under 60 who don’t know anything but the celebrated part of JFK’s history.
This article provides one of the greatest tributes to Rush Limbaugh I’ve ever read. “If Rush had been on the air in 1960-63 he’d have strangled the JFK fable in its crib.” Did anyone read the article?