James Green, a self-described “activist scholar” whose view of organized labor’s violent birth challenged conventional visions of America as a classless society, died on Thursday in Boston. He was 71.

The cause was complications of leukemia, his son, Nicholas, said.

Professor Green taught at the University of Massachusetts, Boston and wrote six books and countless articles, but taking his cue from a Yale mentor, C. Vann Woodward — to pursue history “with a purpose” — he did not confine his interests to the academy.

For decades, he participated in protest politics, including the civil rights movement, and organized community history projects and training programs for labor unions.

“My purpose was to study the past to understand injustice in our society and then to explain how men and women who suffered from injustice gained the will to struggle against it and to strive for a better society,” he wrote in an online autobiographical sketch. ...