The first stop on Sheen’s “My Violent Torpedo of Truth/Defeat is Not an Option” 20-city variety show started Saturday night with thunderous applause but ended 70 minutes later. In between, Sheen tried to appease his audience with rants, a rapper and a question and answer session, ultimately concluding the first show was “an experiment.” The former “Two and a Half Men” star learned firsthand at Detroit’s 5,100-seat Fox Theatre that show business still requires a show. The debacle called into question the fate of the nascent tour. Some fans already predicted a premature end for the monthlong trek, which was scheduled to resume Sunday in Chicago. Sheen, known for his wild partying and rampant drug use, said he thought Detroit would be a good place to tell some stories about crack cocaine. The remark prompted loud, immediate boos. At another point, Sheen showed a short film he wrote, directed and produced years ago called “RPG.” He sat in the front row to watch the flick, which starred a much younger Johnny Depp. Again, more boos. The show actually started off with a bang.