I'm sorry you feel that way. Maybe when you get more life experience, you'll realize that most scumbags will only avoid engaging in heinous acts if the deterrent for doing so is appropriate.
Let's say we do decide to torture murderers. Who is going to torture them? Are we going to pay for these people to have therapy (because they're really going to need it)? How would you feel if you found out your next-door neighbour tortures people for a living? What do we do when we find out, years later, that we've been torturing an innocent person?
I think you need a little more life experience so you can realize that things aren't as simple as you seem to think they are.