WASHINGTON—President Trump hosted a cage match at the White House on Sunday, turning the historic South Lawn into a sporting arena where fighters pummeled each other, surrounded by paid advertisements and thousands of fans. The unprecedented event used some of the most iconic symbols of American power—the U.S. military, the White House and the Lincoln Memorial—to promote the Ultimate Fighting Championship , a company that stands to profit from the fight’s far-reaching exposure. Critics decried the event as gruesome and unbecoming. But the crowd—a mix of military service members, administration officials and Trump allies—reveled in the unabashed masculinity of the…