We talk to filmmaker Callum Macrae about The Troubles, the low-level war that rocked Northern Ireland for much of the latter half of the 20th century. Macrae’s film, The Ballymurphy Precedent, which recently premiered in the U.S., tells the story of the little-known 1971 killings of 11 Catholics in Ballymurphy, a poor neighborhood in West Belfast. Macrae sets the context for the documentary: a political dispute over who should rule Northern Ireland that pitted...