I do tend to agree with the theory that violent computer games have taken away a sense of responsibility, caring, and morale fibre from our children.
However, I recall children, especially the boys of course, in the distant era of the 1950's playing cowboys and Indians, using rifles along with very realistic hand guns to "kill" the enemy. King Arthur and his knights encouraged them to fight to the death with swords, and being so close to the end of the Second World War there where constant 'battles' with the Germans, the filthy Hun who must be 'killed'. Battles also took place in the boys imagination in the air, flying Spitfires, or bombing Germany in Wellington's or Lancaster's. with maybe the odd major sea battle thrown in for good measure. All this was backed up in many comics and pure 'war' magazines, with the general theme of killing the enemy, often backed up by the (male) adults telling of WW2 battle "glories"!
So did that start it all off? Did a whole generation of boys go out and grow into killers? The answer is no. So why should modern youngsters, including girls now, decide to imitate computer "killers"? After WW1 there was utter horror of further war, and thus killing. Following WW2 adults that I knew were all shattered by war, and were completely committed to steering their young away from that terror, although stories were told, many times though to illustrate the complete utter waste that it all caused and the many friends, relatives, lost.
Since then we have had the Korean War, the Vietnam War, the Falklands War, and then the various wars in the Middle East, with us still in Afghanistan. The message, with now constant modern media intense support, showing bodies and all manner of destruction, is of the waste of war, the wrecking of lives and how war achieves nothing.
So again, why would our youngsters still wish to carry out violent actions, including killing?
Is it though all purely down to man's nature, his desire, especially in his youth, to commit to warre (yes, it is Thomas Hobbes theory again!), as though peace is a rare condition, and warre in their minds is the over powering method of curing all problems? Young blood needing to prove they are a warrior of some worth? Some join the military to work that desire out and fight real warre. Others roam the streets needing that "fix" of a good fight, to prove their manhood. Perhaps they too need warre to drain all that desire out?