The bane of the Federal Communications Commission, shock radio exploded on the American scene in the closing decades of the twentieth century. Some hailed this format as a refreshing example of free speech at work—its very outrageousness proof that any message can be disseminated over America's airwaves if there is an audience willing to receive it. Others decried the success of shock radio as a sign of the coarsening of the nation's popular culture—and pointed to its origins in broadcast hate speech as evidence of its secretly poisonous nature.

Shock radio has a thousand fathers (all of them illegitimate, its detractors might add). From the mid-1920s to the 1940s, Father Charles Coughlin spewed anti-Semitic, pro-Nazi, and crypto-Fascist venom to an audience of millions via his national radio program. The so-called "father of hate radio" was one of the first broadcasters to divine the...