Joe Wright’s Darkest Hour butchers history to make the British prime minister a much less decisive figure than he actually was. Because an irresolute and small-minded age applies its own neuroses backward to history, because actors love to portray internal torment, and because we fancy ourselves so sophisticated that we know the official story of the past to be a ruse, movies about important historical figures have become less inspiring and “more human,” at times even iconoclastic... Now it’s Churchill’s turn to be shrunken down to a more manageable size. In Darkest Hour, which is set across May and June...