Well of course society impacts the individual, and this is intentional.
Yes, we need to change society and our own culture to root out problems within it that ultimately harm us as a society and individually.
There are, however, people who do not wish to participate in society according to the rules. Some are harmless. Some are not. Society has a self interest in excluding harmful people from itself.
Sometimes these harmful people are fully and completely a product of society. This is cyclical society destruction, and we have to work really hard to get rid of those teachings and concepts that produce such people. But they are rare.
Then there are people who would not fit into society even if society didn't harm them with poor teaching and concepts.
Some people, and I suspect
Charlie Don't Surf is one of them, believe that the latter group do not exist. That a human newborn is essentially a blank slate, and if the correct programming is taught then they will never have a desire to hurt another human being, or society.
While I believe that the environment, teaching, upbringing, etc has a huge role in a human's desires and motivations, I believe that humans have inborn desires and motivations and are distinctly different from other humans at birth, and its upon that foundation that society must build.
Further, each of us is very different chemically, and while some of this is environmental (you are what you eat, breathe, and absorb) some is genetic. There are some who suffer from significant mental health problems who may not ever be able to adapt to society, even with medical help.
This persons behavior doesn't suggest, to me, a problem that is any less than a mental disease. I'm sure those around him recognize it, but he probably showed enough understanding to refuse psychological counseling, and he himself chose to plead guilty without asking for a guilty by reason of insanity plea which is probably what he actually deserves.
He is sick. He has no interest in being helped.
So all we can do is take his note to society, inscribed in the blood of others, as a sign of his desire to live separately from us.
And he will, until he gets help, or he dies.