Interesting question. The thing is, while Jesus said to forgive, I do not think that He meant that we should not pursue justice for others. The forgiveness issue is, in my opinion, more of a one-on-one, individual issue. As in, you wrong me and I am required to forgive you. Does that mean that we as a society are not allowed to protect ourselves? To take an attitude of "forgive and forget" as a system of dealing with criminals would be ludicrous. We would be overrun with crime. Jesus spoke of forgiveness between Christians, but He also spoke of taking care of one another within the community. He indicated that if a person was intentionally doing harm to others and refused to change his ways, that person was not good for the community and should be expelled. In a society which did not have the sort of jail system that we have now, I would say that was a pretty close equivalent. This person is a danger to our people, so he needs to leave. God expects us to forgive, but not to be stupid. A woman in an abusive relationship, for example, is allowed to leave her husband. She should still forgive him, but that doesn't mean she has to allow him to keep hurting her. I think the same principle applies in your question.

Let's examine the Bible For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins. - Matthew 6:14-15 This seems to suggest that one should forgive. However, this, You snakes! You brood of vipers! How will you escape being condemned to hell? - Matthew 23:33 is most certainly not in the spirit of forgiveness. Also, it seems that certain actions are inforgivable: But woe to that man who betrays the Son of Man! It would be better for him if he had not been born. - Matthew 26:24 Let's confuse things with some Luke (23:33-35): When they came to the place called the Skull, there they crucified him, along with the criminals--one on his right, the other on his left. Jesus said, 'Father, forgive them, for they do not know what they are doing.' And they divided up his clothes by casting lots. The people stood watching, and the rulers even sneered at him. So, we see a bunch of apparent contradiction over this matter in the Bible. I personally believe that the Bible is suggesting that there are two realms of "bad" actions. Those that are secular or foolish in nature are forgivable. Those that are directly against God itself are not. The point of jail is twofold: prevention and rehabilitation. Prevention: it prevents further crimes from happening. If prisoners were merely punished, they would turn to crime again. They need to be detained until they are less of a threat to society. Rehabilitation: one goal of prison is to allow convicts to improve themselves. Jail, for example, is where Malcolm X found his faith.

I remember reading something about it is allowed that we have rulers and governors whom judge our social behavior. Therefore, in a society of God fearing citizens, we elect those who we want to govern our actions and behaviors and adhere to their judgements and punishments. It is not a sin to judge and punish if that is the lot life (and society) has cast for you. And I recall Jesus saying that we should respect and obey our leaders.