Media violence is a big problem. We need to counter this in our homes by providing children with an alternative reality - one where they learn concrete, practical skills. When children discover that they really can resolve conflicts peacefully, and when they watch their parents do this, the alternative reality starts to take shape. Children need to learn the skills of peacemaking in their own homes - otherwise what they see in the media becomes the only reality they know. Also, curtail TV viewing.
Studies have shown that the more TV children watch, the more aggressively they tend to act.
This relates to all TV viewing, not just violent shows. Of course it's also essential to drastically curtail, if not eliminate, violent TV, videos, and computer games. As soon as they can communicate. You can start by eliminating put-downs, catching your child in the act of doing things right, using appropriate praise, and modeling peacemaking in your own relationships. I messages are a honest yet respectful.