To play devils advocate, video gaming produces as much, or more, dopamine than cocaine. I game full time; if i had to guess, i would say between 35 and 40 hours during the week, more if a new game drops (skyrim is going to lose me some friends), and typically about 20 hours on the weekend.
I primarily play fps's, and love open world whole sale slaughter type games(prototype, gta and its clones, hell ill drive around on apb for hours running over pedestrians). I can honestly say i have never shot up a mall food court, or any other public locations, despite being the proverbial lab rat they feed 17lbs of artificial sweetener.I find it all very entertaining, not exactly motivational.
Are video games addictive and potentially harmful? Absolutely, who would argue that dopamine does not cause chemical dependancy. Addiction in any form can be detrimental to your social and professional life. But to say it makes you a killer is a massive stretch.
It is my belief that crazy people will always look for something to blame the crazy on. There have always been serial killers, murderers, and rapist; with the sheer volume of people in the world, i am quite surprised at the infrequency of public shootings and bombings. As a society we are significantly more intelligent and knowledgeable, individually however....well, I'm expected that apocalypse any day