The cancellation of a speech reflects an intense debate on the left: Is racism the primary problem in America today, or the outgrowth of a system that oppresses all poor people? Adolph Reed is a son of the segregated South, a native of New Orleans who organized poor Black people and antiwar soldiers in the late 1960s and became a leading Socialist scholar at a trio of top universities. Along the way, he acquired the conviction, controversial today, that the left is too focused on race and not enough on class. Lasting victories were achieved, he believed, when working class...