To accurately judge history, we must first take a step back and remember that our world is vastly different from that which we are studying. This biography is by no means a romantisized re-telling of the story of Jesse James. In anything there is bias, but not very much exists in this Biography.
That said: Rules, ideals, and society are different in the times of post-Civil War. James believed whole-heartedly in the Confederacy. He fought for his beliefs like any person who is passionate about their beliefs would. He fought with all his heart. Tactics may change from person to person, but dedication is still there.
To say that this biography supports murder and robbery is asinine. It was an interesting, accurate account of a life when times were different. Society helps mold us into the people we are and this is no different for James.
History is written by the winners. How different would this biography of Jesse James be if the Confederacy had won? Would Jesse James be as infamous as he is without the Union's triumph?