This week, millions of American readers fell into silent despair upon learning that Atticus Finch, an iconic if fictional race liberal, was not all that he seemed. For decades, we’ve known him as the literary hero who stood down a lynch mob and defended a black man against spurious rape charges in Depression-era Alabama. He was the righteous lawyer—the enlightened Southerner—the widowed father whose selfless devotion to his children embodied manhood at his best. He was Gregory Peck, for goodness sake.

Imagine, then, how profoundly disheartened his daughter, Jean Louise Finch, was upon learning that Atticus had joined the Maycomb County Citizen’s Council—the hometown branch of the White Citizens Council, a loose organization that sprouted like weeds throughout the former Confederate states in the immediate aftermath (and in defiance) of the U.S. Supreme Court’s decision in Brown v. Board of Education (1954).

“‘Citizens’ council? In Maycomb?’ Jean Louise heard herself repeating fatuously. ‘Atticus?’ … She knew little of her father’s presence at the table with a man who spewed filth from his mouth—did that make it less filthy? No. It condoned. She felt sick. Her stomach hurt, she began to tremble. … Every nerve in her body shrieked, then died. She was numb.”

As we untangle the history behind Harper Lee’s old, new novel, Go Set a Watchman, it seems increasingly likely that the author never intended her first draft to see the light of day. It raises too many discrepancies with her better-known masterpiece, To Kill a Mockingbird, to be easily reconciled as a sequel or prequel. In Mockingbird, Tom Robinson is convicted. In Watchman, we learn that he was acquitted. It’s hard to believe that Lee would not have corrected this critical divergence. In this sense, literary critics are left with enough bows in their quiver to salvage the reputation of Atticus Finch.

For historians, however, the truth is less heartening. There is little reason to doubt, and every reason to believe, that a respectable Southern white man in the 1930s could defend a black man wrongly accused of rape, but still rise to the defense of Jim Crow. To understand why this is so, we need only look to a real instance of Southern injustice—the ordeal of the Scottsboro Boys—and to Grover Hall, a real-life newspaper editor who championed their cause for reasons more complex than a Hollywood film. ...