There is a lot of debate about media violence, particularly in its effects on children. Although no one really claims that all problems with aggressive kids are caused by violence in the media, everyone knows that it does have some affect on some people. The real question comes down to a chicken or the egg sort of thing: we know that violent kids and young adults tend to be more interested in media violence than most people, but we don't understand the cause effect relationship. Are these people interested in violent programming and games because they are violent people, or do they become violent people because of their interest in violent media?
Some parents take a very aggressive position on media violence. I know a few families that will cut off the access their children have to any but the most nonviolent and nondestructive media. They claim that, through limiting exposure to Hollywood movies, violent music, and video games, they can make their children grow up to be more peaceful, productive people. This approach requires a lot of sacrifices and very vigilant parenting. It is hard to live in a modern urban or suburban environment and restrict your child's access to the media.
Then again, there are other people who focus more on violent behaviors and aggressive emotions than on media violence per se. This has always been my approach personally. Rather than trying to limit what my children watch or what games they play, I try to help them engage in activities that will make them feel more peaceful and less prone to anger. By making sure my kids get enough exercise, do meditation and yoga, and feel comfortable talking about their feelings, I can help them become more psychologically healthy and happy. In my mind, this is probably the best antidote to living in a violent society.
I suppose that, no matter what your position, the important thing is to show that you care. All parents make mistakes, and even your whole approach to violent programming might be the wrong one. Nonetheless, by doing your best to take an active role in your child's life, you are showing that you are interested in what happens to them. Just by taking the time to care, you really can change things for the better. Not every parent knows what to do, but every parent knows they have to do something. This is the first step towards being a good parent and a good role model.