“The Flamethrowers” captures the punch-you-in-the-mouth energy and sound of right-wing talk radio. Host Justin Ling takes us from the fringe preachers and conspiracy peddlers of the 1920s to the political firestorm that rages today. With humour and candour, Ling examines the appeal of broadcasters like Rush Limbaugh, who found a sleeping audience, radicalized it, and became an accidental kingmaker — culminating in the election of Donald Trump.