Donald Trump, who will be sworn in at noon today, graduated from business school in 1968, the same year Martin Luther King Jr. was assassinated. The two men never met, and yet at times Trump has obsessed about King’s legacy — or at least about how the size of the crowd that gathered on the National Mall for King’s “I Have a Dream” speech compared to Trump’s speech on Jan. 6, 2021. What would the nation’s great civil rights leader, whose birthday is traditionally celebrated with speeches and ceremonies and a day of community service, think of sharing this day,...