If Loughner did commit this crime because of political motivations, he is certainly to blame. His political motivations are also under the control of his own free will and thinking. If he is chemically unbalanced, this complicates the matter as to his motivations. But if the question is what motivated him to do this, it seems like political beliefs had something to do with it. Some media commentators and political pundits have condemned other politicians on the right for encouraging outright disgust for those on the left, but you can’t place the blame solely on any political faction; regardless of what they say. The underlying problem is the growing bipartisanship and separation of the right and the left in America. This dialectic or binary opposition has been overblown and in fact, encouraged on every political talk show and elections themselves. The fact is that the right and left are not always inherently oppositional, but media and politicians themselves have wholeheartedly endorsed this idea to the point where they view the “other side of the aisle” with scorn bordering on hate. This binary separation comes from a historical and philosophical tendency to think of the world in terms of black and white. It is cliché but a fact about human history. Public/private, Man/woman, Social/Individual, Good/Evil – Separating concepts in this way has tended to reinforce thinking of the world in such ways. If you believe in one philosophy or politics, the other ‘seemingly’ oppositional side of politics must be evil, because your way must be the good way. It is simplistic, lazy and fundamentally false thinking. So, Loughner committed the crime because he may be crazy, easily influenced and definitely lacked the ability to think critically about political science and ethical behavior. But there will be conversation (or there should be) about the mindless opposition that exists in political discussion; and how such ‘us against them’ fundamentalist thinking won’t make someone commit a heinous crime, but that such thinking reinforces a polarity in politics which really doesn’t exist and prevents the right and left from compromise and actually achieve progress.
Politics has fallen victim to what's called a false dichotomy. (link)