We need to answer the why, to confront the cause. Of course, as in all of these types of heinous acts, the why is not singular. He was obviously mentally ill and didn't get the help he needed, even after so many saw the warning signs. And, that is a conversation to have. He was mentally ill and had easy access to a handgun that is made to kill quickly and easily. That is also a conversation to have.
The evidence of the nutjob mass-murderer's politics point, in my opinion, to a libertarian/anti-government/racist leaning. There is a lot of cross-over between the libertarian-anti-government-conspiracy-racist-isolationists and the tea-party-anti-government-racist-isolationist. I don't think is really matters if he was a card carrying member, or follower of any specific political ideology. Honestly, I don't think he is capable or aware himself of how to form a consistent political worldview.
The question is whether the politics of hate from the right and the violent rhetoric of tea-party encouraged and fertilized the damaged, squishy mind of someone already deluded with hate. Had he not been in an environment that fosters hate-speech as a legitimate dialogue, would he have acted the same? It is a question that will be hard to answer. It can really only be answered if he was honest about his motives and what lead him to kill. It is not out of the realm of possibilities that he would have flipped and killed anyway, perhaps at his school or elsewhere. Not that a school shooting is in anyway less tragic. However, school shootings don't elicit political responses and aren't labeled as assassinations or terrorism. Political targets have a unforeseeable fallout, a shock wave that ripples across our country.
Did the hate-speech of the right lead him to a political target?
Included is a crude Venn diagram of libertarianism cross-over. It is ron paul-centric, but the idea is the same (it was the only one I could find, and I don't feel like making on tonight).