Personally I think a bad prophet is an oxymoron. A bad prophet by definition is wicked. I don't believe that true prophets of God can be wicked. My idea of a prophet is someone who is God's prophet on the earth and speaks for Him. God only will use righteous people to represent him. Therefore I don't think there are bad prophets. There might be wicked people who claim to be prophets, but in my mind they are not prophets - just evil and wicked.