If America were a song, the killing of unarmed black people by the police would be a standard chord progression or rhythm, the sort of indistinguishable background noise that you hear so often you might not even notice it anymore. On Friday, in Tulsa, Oklahoma, a 40-year-old black man named Terence Crutcher had car troubles. The police approached him. Crutcher responded by putting his hands in the air. The Tulsa police used a Taser on Crutcher. A Tulsa police officer, Betty Shelby, then shot him dead. They left him bleeding in the street for almost a minute before rendering any...