A worthwhile article whose title is misleading and whose conclusion must be placed in context.
The article involves about 200 kids whose media diet is calculated and whose proneness toward aggression is then evaluated through perceptions of their teachers. The conclusion is that kids who watch about 1 hour or less of violent media per day may actually be less violent than the average child, but children who watch three hours or more of violent media not only are more prone to aggression but also likely to perform more poorly in school.
So the problem here is that most kids watch far more than one hour of media per day, and further much of this involves violence. In fact, kids at this point in the early 21st century watch on average about 5 or 6 hours of media per day. The kids who are watching an hour or less a day are the exceptions and are immersed in other interests, like sports or out of door hobbies, or studying and reading, or ones who have many friends who themselves may be less prone to over-immersion in the media.
It’s the ones who are more immersed in media and specifically in violent media who are of greatest concern, and they are the ones who this study suggest are more likely to manifest aggression in social settings.