Well teenagers are not the ones usually mimicking what they see on television, it is the children. If they were predisposed to violence at a young age, whether it be from parents fighting to shootouts and wrestling on television, they are more likely to express aggressive behavior.
Furthermore, I would say sex in the media is affecting teenagers more than violence. With all the different sexual messages that they are constantly bombarded with everyday, and popular culture promoting an unequal gender relationship, teens don't really have much of a choice but to go with it.
