I think you guys should take this study a little more seriously, study into whether or not game content actually causes violence is incredibly important if we are ever to squash that opinion, yes the outcome may seem obvious but the fact they reached that outcome via a real study justifies it completely.
The thing is, this effect is relevant to everything we do, from Pokemon to football to your day job, failure and a feelings of inadequacy or incompetence effects everyone and in very different ways.
Also, the study is not saying the aggression caused by this leads to murder, just that aggression is more likely caused by the mechanics and/or success in games rather than as an effect of their content.