The Tragedy is Us...
I know this may seem like sympathy for evil, but that's not how I mean it. What I mean is that there are few, if any 'monsters' among us who have not had the same evil they inflict, inflicted on them and usually when they were innocent, vulnerable and impressionable children. Ariel Castro said 'I was abused as a child' and typically he did not elaborate, because for most victims of childhood abuse, discussing it is all but impossible.
There is no justification for what Castro did, but there is also no justification for our society mocking and demonizing him and taking pleasure in the knowledge that our dysfunctional justice system would have allowed his fellow prisoners (also misguided victims) to torture and abuse him.
We're not studying and learning from these tragic cases, we are simply punishing to satisfy our own angst and hate.