One of the difficult but primary duties of the modern presidency is to speak for the nation in times of tragedy. A space shuttle explodes. An elementary school is attacked. The twin towers come down in a heap of ash and twisted steel. It falls to the president to express something of the nation’s soul — grief for the lost, sympathy for the suffering, moral clarity in the midst of confusion, confidence in the unknowable purposes of God.Not every president does this equally well. But none have been incapable. Until Donald Trump.Trump’s reaction to events in Charlottesville was alternately trite (“come together as one”), infantile (“very, very sad”) and meaningless (“we want…