Far more sober and reasonable than its shouting-in-the-streets title suggests, Cory Taylor’s JFK: A President Betrayed plays out like what you probably wish the History Channel was actually like: Over arresting period footage, historians and actual participants in the history recount in intimate detail the behind-the-scenes wranglings of presidents, premiers and their advisers. Rather than doling out scandal and conspiracies, Taylor focuses on the one thing so often unmentioned in discussions of our first modern celebrity president: actual policy. The film traces the young president’s foreign policy adventures, from summits with Khrushchev to the Bay of Pigs disaster to the Cuban Missile Crisis, where Kennedy rejected the plans of hawkish advisers to hit Castro’s island with a Normandy-style troop invasion. (A good thing, too, as the Soviets had tactical nukes ready on Cuba’s beaches.) The betrayal promised in the title is twofold: First, those same hawks balked as Kennedy moved toward policies of peace and disarmament, sometimes secretly working against him. Second, Kennedy had resisted the deployment of U.S. troops into countries targeted by the Soviets, especially Vietnam; after his death, of course, the Johnson administration went whole-hog in the other direction. The film offers a solid précis, but it’s a curious fact that a well-made doc like this is still only about half as informative or detailed as a long magazine article on the same subject might be.