Yes, violence in the media promotes violence in real life.
Dahlia Lithwick, writing for Newsweek in 2008, regrettably calls 24 hero Jack Bauer (played by Kiefer Sutherland) both "the prime mover of American interrogation doctrine" and "the most influential legal thinker in the development of modern American interrogation policy."
Lithwick bases this conclusion on two recently published books: Jane Mayer's The Dark Side: The Inside Story of How the War on Terror Turned Into a War on American Ideals and Philippe Sands's Torture Team: Rumsfeld's Memo and the Betrayal of American Values. She writes that the legal team establishing U.S. policy, including primary author John Yoo, had a tendency to cite Bauer more often than the U.S. Constitution. Also, that people within the Bush administration, such as United States Secretary of Homeland Security Michael Chertoff, as well as military personnel at Guantanamo, consistently drew inspiration from the fictional Bauer's cutthroat techniques.
It's a real problem that the cultural agenda is set by a small group of people who are not operating with the best interests of society at heart. I know for a fact that many people who work in media are flip, shallow people, who have contempt for the viewers.