One of the most emotionally charged moments of the last night of the Democratic convention came when the father of a Muslim American soldier killed in the line of duty took the stage. Humayun Khan, 27 years old when he died, was a graduate from the University of Virginia and a captain in the US Army when a suicide bomber attacked his unit in Iraq. He died protecting his fellow soldiers. On Thursday night, his father, Khizr Khan, gave an impassioned plea to the American people to vote for Hillary Clinton—and delivered an even sharper rebuke to Donald Trump.