The principle is stupid. People say that violent games influence aggression as people try to recreate what they see on the screen or it is normalised to them. If we accept media has this profound effect then we accept it does so outside of just violence. A good example someone gave me is by the same logic people should be trying to inflate their heads to look like wii-me's or jumping off buildings to land without damage (a la every superhero/super villain game). If they recognise a disconnect between this media and reality, it follows they recognise a disconnect in more 'realistic' media.
It improves stimuli more in men - specifically the hunter/gatherer instinct - but in doing so actually reduces manifest violence and aggression as these natural biological instincts are catered to in a safe, sheltered environment. It gets it out of the system so to speak.
The societal problem of violence, particularly with minors, is due to the ridiculous amounts of freedom children are given and a lack of strong parenting. Kids are held up on a pedestal for no adequate reason and - as kids do - they push boundaries. When nobody pushes back they continue to push. This is how children learn. When the law slaps them on the wrist and their parents don't care, are too busy working or are otherwise absentee they have no strong guidance (particularly due to the breakdown of the family unit and prevalence of single parents in the modern era). It is more complex than that but this is a simple summary of the myriad of problems which lead to the outcome of violence, the blame is shifted to video games because its easy to scapegoat and those in power (middle/upper class) dont play games, they rent racetracks, go skiing for a weekend etc. They have no need of them and thus any negative impact on the medium doesnt affect them.