Paul Johnson tells the true story of Sam Patch, a man born into poverty in the early 1800s. As an adult, he gives up his job working in a factory and becomes a stuntman, and became widely renowned from jumping off bridges.
The first public jump that he makes is a protest against the exclusion of working-class people from a nature reserve that is to be opened in Paterson, New York. While Sam starts to make fairly good money off his jumping stunts, Johnson makes it clear that all Sam's jumps were made to draw publicity and attention to the plight of his fellow working-class men and women.
I would argue that Paul Johnson had an easy job of making a convincing argument about Sam Patch's political statements. Basically, all Johnson had to do was tell the stories and explain what happened. Sam Patch's message spoke for itself because he became so well known for his stunts. It's hard to ignore a man who makes a habit of jumping off bridges. It was Johnson's choice of subject matter, therefore, rather than a specific storytelling method of Johnson's, that made this message so powerful.
Even Sam's untimely death, caused by yet another jump attempt, adds impetus to his message of equality for working class people.