If you read Harper Lee’s “To Kill a Mockingbird” in high school, you probably recall it as a parable of racial injustice in the Jim Crow South. It was more than that. The novel chronicles the persecution of an innocent man by a bigoted and bloody-minded town. Amid the left’s crucible of Judge Brett Kavanaugh, Lee’s enduring lessons about due process merit reflection.

The story is set in the sleepy fictional backwater of Maycomb, Ala., in 1935. A black man, Tom Robinson, stands accused by 19-year-old Mayella Ewell and her father—lower-class...