Regarding the Batman movie massacre: What is behind the obvious and all too frequent disconnect between the objective truth, and the shameless and subjective desire to manufacture truth?

A lunatic dresses up in dark clothes and Kevlar, carries guns into a movie theatre and kills and injures dozens of people. Immediately, the various producers of news product announce that he:
Is a Tea Party nut job
Might be an OWS fanatic
Could be a Muslim terrorist
Could have been thwarted with more strict gun laws
Could have been thwarted with more liberal gun laws
Represents an aberration that will go away if we ban Batman movies
Would not have been a problem if theatre owners would have imposed a dress code
Etc. etc. etc.

Everything you can imagine except the obvious.

The guy was fucked up beyond all recognition, and he decided for reasons we can never totally appreciate to randomly kill some people. Plus, he was not a recluse (he was a student) and thus people have interacted with him and it is reasonable to assume that at least one of them knew he was fucked up and said nothing.

So WTF is this post-modern tendency to try to come up with excuses for people’s bad and/or stupid behavior in order to avoid admitting the obvious?