"Precisely," said the general. "That is why I use them. It gives me pleasure. They can reason, after a fashion. So they are dangerous." (1.123)
Let’s break this down: Zaroff sees reason as a crucial ingredient of competition and the ultimate way of creating danger. He may enjoy the psychological warfare more than the actually physical harming bit. Should this change how we feel about him? Does it make him a darker figure? A less bloodthirsty one?