James' real world politics and his mythology arent exactly te same thing. Did folks writing books and movies about him dwell on his pro-Confederacy or pro-Slavery stances? The image they promoted was as a Western Robin Hood. McPherson's review seems focused on the way the book scraped away the myths and exposed the real Jesse James.
"Among all the myth and folklore as well as the serious studies of Jesse James, this book stands out as the best account of the meaning of his life and times. James was neither a Robin Hood figure nor a 'social bandit' nor a 'primitive rebel' nor an emblem of rural America's last stand against capitalist transformation. Rather, James and his associates were Confederate guerrillas who, in a Missouri torn by the Civil War, kept up their battle against the victors for a decade after. For the first time, thanks to T. J. Stiles, we see the real Jesse James."
--James M. McPherson, author, Battle Cry of Freedom