Past the towering tridents that survived the World Trade Center collapse, adjacent to a gallery with photographs of the 19 hijackers, a brief film at the soon-to-open National September 11 Memorial Museum will seek to explain to visitors the historical roots of the attacks. The film, “The Rise of Al Qaeda,” refers to the terrorists as Islamists who viewed their mission as a jihad. The NBC News anchor Brian Williams, who narrates the film, speaks over images of terrorist training camps and Qaeda attacks spanning decades. Interspersed with his voice are explanations of the ideology of the terrorists, rendered in...