It also doesn't go any good. Evil begets evil. You can only break the cycle by doing good.
I saw a show the other day, about a serial killer. At his trial, they let the families of the victims come up and speak to the guy, in front of the courtroom. All of them condemned him, cursed him, and railed at him, but one man. One elderly, white-haired old man that had lost his beautiful, young daughter, came before this gathering of vengeful people, and said something that finally got through to the serial killer. He forgave the killer, and that was the first time, throughout all of this time, that the killer had showed any emotion. The emotionless psychopath broke down and cried when he was forgiven but this crying old man.
I strongly believe the killer expected condemnation, was prepared for it, welcomed it. It would only fuel his conviction that he was different, that he had a duty as a 'predator' to cull the herd so to speak. But the old man totally brought my point home.
You can visit evil upon evil-doers all you want. All it will do is continue the cycle of evil. Sometimes, you might have to break down, forgive them, and try and help them. Sometimes these evil people are just sick people, but you can't tell because they've hidden their sickness behind their violent, cruel acts.