Since his wife of two years, Angelina Jolie, filed for divorce on July 17, Billy Bob Thornton has been keeping his mouth shut -- except for singing in support of his CD, "Private Radio." USA Today reports that last weekend the "Monster's Ball" star, 47, and his band performed at the American Heart (Association's) Awards at Southern California's Beverly Hilton Hotel, his first public appearance since the dissolution of his fifth marriage was announced. He opted to enter the hotel via a back door rather than face the media out front on the red carpet. Onstage, though, Thornton, outfitted in a black sleeveless T-shirt, black jeans, a shiny black beanie and his signature cowboy boots, was outspoken with the black-tie crowd, according to the newspaper. "I know there are a lot of doctors in the audience tonight, but I did write a song about pot," he said. "I'm sorry. It's a song that's a tribute to my old buddies who used to lay around and watch cartoons and smoke dope all day." He also said, "We're not normally used to playing this type of venue. We're usually with a lot of very slutty people. Very slutty people who are dressed even worse than we are."