http://www.mediafamily.org/mediawise/index.shtml
the violence is pointless, and its very presence is confusing to kids who are (hopefully) being nurtured with every kind of gentleness we can provide.
adults can enjoy the violence, as cathartic or vicarious release of tension, etc. There is just no context for that for kids, and no reason to force the harshness of the world on them at the age of 4