It seems to me that it's just another excuse to focus the blame on something other than the parents. It's kinda like what happened at Columbine, where the parents were trying to blame Marilyn Manson, for personally contributing to those boys' actions. If they really would have focused more on their kids, then maybe that tradegy could have been preventable, but you know what they say, hindsight is always 20/20......
It may be true that playing violent video games may increase the chances of aggressive behavior, but if the kid can't distinguish fantasy from reality, then he should have been treated for some type of mental illness a long time ago. The kid was obviously delusional, and yet the parents never noticed any out of the ordinary behaviors? I mean, how was this kid in school? Has he been in a lot of fights, or displayed acts of violence before? It seems like there are many parents in denial, and they don't even want to fathom the concept that their kid might have some serious problems.
The whole point of the matter is that if your kid can't tell the difference between right and wrong by the age of 17, then the parents some where down the line either did not raise their kid properly, or did not attend to his needs.
That's my opinion anyways....