Freedom, who is Muslim but knew little about the Uyghurs, threw himself into the cause. Tahir Imin, a Uyghur activist in Washington who met Freedom at a Capitol Hill rally, said that Freedom “boosted the morale of Uyghur activism.” That was just over a week after Freedom opened the N.B.A. season with the Boston Celtics, in October. Ahead of their first game, Freedom posted a video on Twitter with a caption referring to China’s leader, Xi Jinping, as a “brutal dictator.” During the game, he wore shoes designed by the…