the notion was that criminals are a product of society, and the cure lies in constant correction and reformation of us as a whole rather than just killing criminals as they spring up, like so many cockroaches.
blame is not the issue, and certainly not the basis of our prison system (the ideal, not the quagmire its become and continues to grow as).
as i said, society breeds its own filth. the root of the problem is not so simple as "kill it or let it live" but rather "dont allow more to be created". in the meantime, while we face this problem, we focus on rehabilitating criminals rather than allowing the fringe ends (gasey, dhamer, manson etc) to justify us crumpling the theory up into a ball, calling it all "liberal crap", throwing it in the trash, and turning our prison system into a system of revenge and gratification for those cheering on the 50 yard line.