Filmmaker John Singleton, who burst to prominence with his 1991 social drama "Boyz N the Hood," says he has to balance his "message" movies with "popcorn" flicks to support his more serious work. In a recent interview, Singleton called this balancing act the "yin and yang" of his life in Hollywood as he promoted his latest directorial effort, "Four Brothers," an inner-city action movie that mixes a little message with a lot of mayhem in a revenge tale with a violent take on family values. Larry Fine reports for Reuters.