Paul Harvey's biography of the "obnoxious child who grew up" was of the late attorney Roy Cohn. Cohn made his reputation as the chief counsel to Sen. Joseph McCarthy in the 50s anti-communist hearings, and continued to do dirty work for Nixon and then Reagan. Most interesting fact - and hypocrisy - of Cohn was that he was able to spend his manipulative career hiding the fact that he was a self-hating homosexual while working as a Republican activist in crushing any progress in Gay rights and quashing AIDS research and study, while simultaneously funnelling the latest medical treatments to himself. [This aspect of his life is the focus of Cohn's character as presented in Tony Kushner's drama "Angels in America", now airing in an adaptation on HBO - with Al Pacino as the very-ill Cohn.]
Harvey is perceived as a "populist" who, especially at his advancing age - even then - is very 'out-of-touch' with modern perceptions (which is sort of the source of his appeal). The joke is that Harvey is soooo out of touch that he gives a fawning, sympathetic portrait of Cohn. Also, Harvey's 'profiles' on his radio show always follow the format of reciting the biography, and then, at the very end, revealing who the subject is.
Also, btw, the Blue-haired Lawyer is himself modelled after Cohn - in Dan's vocal performance more than his look.