But he's right, it is morally praiseworthy to make wrongdoers suffer. Humans have known this for millenia, we know it deep in our bones. Murderers, rapists, thieves all deserve to suffer.
There is the argument that making bad people suffer ruins our morality. If we're better than them, then we don't want people to inflict suffering.
The act of torturing someone does something bad to you, regardless of whatever other effect. The kind of person who would torture someone in cold blood is not someone I want next to me.