The greatest harm to the public in both is when the simulation isn't enough anymore and they move to act it out. Hence the epidemic of grade school kids engaging in shocking sexual acts, 'sexting' and other problems that have engulfed our youth.
Through these media, our kids are taught and stimualted to kill. They seek to rack up the highest scores and receive enough simulator training to effectively point and shoot with devastating results. Years ago I attended a seminar from LTC Dave Grossman (On Killing). I was sceptical of many of his claims, and certainly the media aren't the only factor involved, but over the years and after much study and reflection on the problem, the link is undeniable. These attacks become increasingly costly and the death tolls higher and higher in direct proportion to the increasing sophistication and realism of violent visual media.
Sorry, Mr. Tarantino, but you and your ilk have MUCH blood on your hands, and it isn't colored corn syrup.
Young men in other countries play the same video games and watch the same movies and do not commit as many mass killings as American young men.