The past few years have been marked by a series of extrajudicial murders of Black people by police and vigilantes and by the emergence of a nationwide protest movement loosely united under the slogan “Black Lives Matter.” The Black community and their activist allies have expressed outrage in the wake of the killings of Trayvon Martin, Jordan Davis, Renisha McBride, Eric Garner, Michael Brown, Tamir Rice, Walter Scott, Freddie Gray, and many others, and have organized rallies, vigils, and direct actions in cities across the United States. Black Lives Matter has sought to...