You are doing something bad to him because he did the same to you.
You hate him for that ,you considered him evil will you hate yourself too?
Will you consider yourself evil too? Because you did the same thing that he did to you the thing that you considered bad.
Prison guard tortured the prisoner for many years one day prisoers took control over the prison they caught all the guards. All the prisoners have lot of anger in them one suggested that they should torture the guards as they torture them other asked that if he hated guards for that he said yes than the other one said that would you not hate youself then because you are doing the same thing that they did to him one knocked this one out and they tortured the guards.