I'm seeing that a few folks are talking about completely different things and seem to think the other is contradicting them. Halfabo is talking about the effectiveness of punishment fitting the crime, when it comes to laws governing society. What others are talking about is the need for forgiveness.
Let's be clear. Jesus spoke of an eye for an eye because He was specifically raising a point about the Old Testament, Mosaic Law. The initial reason the law was established was to instruct the Israelite leaders on how to dole out punishment for crimes. However, the result was, the Israelites themselves started using that law as "justification" to pay someone back for what they deemed as the other doing them wrong. Then the recipient of said payback, would claim they were the one being wronged, and return the favor. And back and forth it went, in an endless, escalating cycle until finally (if I may take the liberty of supposing), what started as a neighbor kicking the other neighbor's dog, ended up in both parties slaughtering each other's entire family and burning their house down.
The only way to end it once and for all, is to nip it in the bud at the very beginning and forgive. But that in no way is a command for the secular lawmakers to practice forgiveness. The law governing general groups of people is to be impartial, blind, and not favoring one religion over another. The only way that works is for everyone to be punished according to their crimes. If the law forgives at1 but then punishes qmark for the same crime, that is completely unfair, so an eye for an eye applied to everyone, is the only way to go. Christ expects the Christian family to rise above all that and just forgive straight away.
"But let us not come up with any patronizing nonsense about Jesus being a great teacher. He has not left that open to us. He did not intend to." C.S. Lewis