From Christopher Hitchens, God Is Not Great, Chapter 8:

If the New Testament is supposed to vindicate Moses, why are the gruesome laws of the Pentateuch to be undermined? An eye for an eye and a tooth for a tooth and the killing of witches may seem brutish and stupid, but if only non-sinners have the right to punish, then how could an imperfect society ever determine how to prosecute offenders? We should all be hypocrites.

I never thought about this obvious conflict when I have read the Bible. I know a similar dilemma arises whenever Immanuel Kant's moral justification for punishment is discussed. According to the German philosopher, a criminal should be honoured the punishment equivalent to the action he is convicted of, which makes one wonder if no one but the victim can perform the actual punishment.