President Donald Trump turned professional sports into a political battleground Friday night into Saturday, directing full-throated ire toward African American athletes who have spoken out against him and prompting a sharp rebuttal from the National Football League and several prominent sports figures. In a span of roughly 12 hours, as the sports world would typically be gearing up for college football and baseball’s pennant races, Trump ensnared and agitated the most powerful sports league in North America and angered NBA superstars Stephen Curry and LeBron James.