"The crucial point is that the dynamics are internal, not external. These killers are primarily the product of psychological derangements, not sociological ones."
It is a common mistake on the left to imagine that sociological propositions about general trends can give insight into specific individual actions and behaviours. But they can't. Some actions are so exceptional that they do not really fall in the scope of sociological analyses, nor are they addressed by social policies (except of course that one needs to fund mental health care).
Mass murder is just too rare - and too small a sample - to make generalisations upon. Were the processes at work in Adam Lanza's head in any way comparable to those at work in Anders Breivik's head? It seems unlikely, even if outwardly their actions look similar.
Obviously it is tempting to force these exceptional events into whichever demonology you are working (I noticed myself momentarily pleased reading that Lanza's mother was preparing for some kind of apocalypse, I am sorry to admit.). But that is to look down the wrong end of the telescope. It would make as much sense to blame the inherent bossiness of teachers; or the coldness of accountants.
Social trends are explicable in social terms. But to kill twenty children, and your mother, outside of any recognisable conflict or struggle is something that needs to be understood in psychological terms, not sociological ones, as Brooks says. These events are too exceptional to tell us anything much about the state of the nation, or any such thing.