much ado about nothingBecause this was the society he was defending. A slave holding and actively enslaving society. Its why the citation: "Lee, man of honor" always has an asterisk.
Lee was always honored by his men and postwar by the South and the American nation as a whole. But the OP is asking us: was he a great general and an honorable man. Great general for sure. But as Shakespeare wrote in All About Nothing "in a false quarrel there is no true valor." Lee's greatest feats were in the service of America's worse cause. We can understand Lee, we can comprehend his social background and ideas and conflicting loyalties. We can respect his courage, commitment, military judgement, leadership, and intellectual daring. But honor? Which, to me, implies approval, justification, righteousness? There will always be an asterisk.