In 1979, members of the KKK shot and killed five labor and civil rights activists in Greensboro, North Carolina. Aran Shetterly, who is writing a book about the incident, says it still reverberates in the racial politics of Greensboro today. Also: The European philosophers of the Enlightenment argued that Europeans were civilized, but Africans were barbarians. Stefan Wheelock describes how radical African American writers used those same philosophical principles to unmask the barbarism of slavery.

Later on the show: One of the darkest pages of American history is the racial terror inflicted on thousands of African Americans through lynching. Gianluca De Fazio and his students have developed a website Racial Terror: Lynching in Virginia, 1877-1927 that focuses on telling the stories of all the 104 known lynching victims who were killed in Virginia between 1877 and 1927, nearly all of them African American men. Plus: Renee Hill coordinated a memorial service to pay tribute to the lives of the thousands of people who suffered lynching in the United States.