Under a legal theory endorsed by the 5th Circuit, Martin Luther King Jr. could have been liable for other people’s violence.In his last protest march, Martin Luther King Jr. led a parade of demonstrators down Beale Street in Memphis, lending his support to striking sanitation workers. After a few young black men started breaking storefront windows, the indiscriminate police response killed one suspected looter and injured dozens of protesters. Under a legal theory blessed by the U.S. Court of Appeals for the 5th Circuit, King could have been held liable for the unanticipated harm that ensued from that March 1968...