Former child star Bryan Hearne, now 35,is speaking out about the mistreatment and racism he experienced as a cast member on Nickelodeon’s sketch comedy series All That in the early 2000s, RadarOnline.com has learned. Hearne, who appeared in seasons 7 and 8 of All That and was one of the few Black actors in the cast, alleged in a new interview with PEOPLEthat he was “referred to as a ‘piece of charcoal’ [by an adult]” during his time on the show. “Remarks like that are harmful,” he said. “They stay with you.” Hearne said that he was often asked to play racially stereotyped roles like rappers an…