I would destroy the book.
Only God can judge people. Only God sees the inner self of a person
and if so however a person is evil. Then that means that person made mistakes which brought him to that status.
And to be killed by a mere person who also makes mistakes isn't right. If you want a chance for forgivness for your mistakes, so does anyone else needs. There is a more suited way to protect mankind to these so called evil people. Things like prisons where someone can think about his/her actions, without harm anyone.
anyway, you can go deeper about the subject or just troll
interesting topic
