The discussion of violence on TV has become very heated and debated indeed. On the one hand you have a group of people who say that we control our own actions and that we are the only ones responsible for our actions (i.e., not parents, television, video games...). Then you have some that agree television violence increases the propensity of a person/child to emulate that violence, but that the effects are short-lived. They also say that violence only increases the likelihood of child violence by minor amounts, that it doesn't actually cause it, per se. Your final group says that television/movie/video game violence is pervasive and undermines the morality of children. They say that even the least violent among us can be pushed to violence by the "rush" they get from watching violence on television. All three points are very important to this issue. Of course, most people lie between one of these three points.
There are a number, however, who adhere religiously to one of the aforementioned points. It's these arguments which are easier to discuss, since a known position is always easier to pin down than a shifting opinion. We may as well start with the last point (since information is more readily available) and progress through the spectrum in reverse. The position is that violence tends to undermine positive behavioral patterns in children/teens due to its pervasiveness. This point deals with several key issues, such as stages of television-watching (and attention span), cognitive processes and reality checks, the end effects, and possible parental intervention. According to Dr. Johnson, television-viewing is split into several different ages. Children under 18 months are incapable of investing the amount of attention required to watch any more than bits and pieces of television, preferring instead to go about their daily activities.