"What we know is that this young man, deeply mentally ill..."
Noooooo shit. In the words of Chris Rock: "Why can't they just be crazy?" People of all ages have been doing absolutely horrendous atrocities for a very, very long time...long before violent games have been around. There's no need to find excuses for them, no need to try and find what pushed them over the edge. The answer's already there: THEY'RE FUCKING CRAZY! Since we're blaming violent games, we better blame violent music too. And the movies, I'd imagine the violence in movie and television played a part too!
Lanza also probably saw violence out on the streets, or heard about it in the news. We better ban all violence in news programs too. In fact, the only way we can prevent these kinds of tragedies is to just go ahead and ban violence in general!
Why is it so hard to understand that crazy people are fucking crazy? That they don't need a source of inspiration before they do crazy things? By all account, Lanza was an absolute fucking psycho. If you've ever seen a picture of the guy, you only need on look at him to say "That guy looks like he's fucking nuts!" His mother had to warn babysitters to never turn their back on him because there's no telling what he could do, he was a dangerous person in general. It wasn't the games, music, or movies that turned him into a dangerous individual, it was the fact that he was completely fucked up in the head. He was a crazy person. We've seen countless crazy people in the past, we're bound to see countless more in the future.
It all boils down to votes. Something terrible happens and the public demands that lawmakers do something. And since you can't ban "being crazy", you need a strawman to burn in order to make it look like you care and that you're trying to prevent such things from happening in the future. Truth is you're never going to be able to prevent such tragedies from occurring, but the general public can't accept that as an answer, and no amount of common sense back by scientific research (as yet another study just came out saying NO FUCKING LINK BETWEEN VIOLENCE IN GAMES AND VIOLENCE IN REALITY) will convince them otherwise. But no, despite the numerous studies already done on the matter - the vast majority of which say "no link exists" - we still need to study it more.
It's quite simple, really, if you can't tell the difference between a game and reality, thus making you want to "act out" the game IN reality, you're already fucked. You're nuts. The game didn't make you nuts, it's just further proof that you ARE nuts.