The justice system is not a law of gravity. It's completely made up by people. And as people change, or change their opinion, the "system" also changes. Of course, our conversation on HN does not change the court system, but both you and me are debating because of expected possibility to change each other's opinion, or someone's who is reading this.

If you are born as black slave girl in 1825 and have a lot of difficulties because of your origin, skin color, and gender, is it "overreacting" to say "slavery is absolutely immoral and beating wives and children is immoral too"? Is it moral to have 50% less slavery and brutality, but immoral to have 51% less slavery because it's too extreme?

Yes, people would like to not waste brain cycles on the security. And there are different ways to do so if you allow competition in that area. E.g. the government does not tell you how strong should be your door lock, therefore you have choice to buy the lock you like and not "waste brain cycles" on it. Same with computer security - you choose a password, stick with it and feel secure. If, on the other hand, government punishes choice and forces people to accept whatever police they set up, then people have no choice, but to accept it and further save their brain cycles. But you cannot derive from that situation that they have chosen this method because they are accepting it. It's like saying that you choose to pay your taxes because of the gov "services". If people were choosing to pay taxes, why need policemen to force them to?

Do you really believe that people somehow come together, debate and make collective decision? In reality, some people who want to debate about, say, taxes, come together and discuss where to spend them to (e.g. roads vs. military). Those who don't like taxes at all are not invited to the discussion because "they are unrealistic". Then, the first group decides somehow to do something, comes back to the second group and forces them to pay taxes "because people decided to". This is a mob rule and not justice in any sense. Do 99 people have a moral right to take away from 1 in a situation when 49 should not take the same from 51? Compare this with corporate bylaws: majority of shareholders may decide over the minority, right? But the difference here is that all of them came together and subscribed to these rules voluntarily beforehand, can exit at any time and are never threatened by murder, jail etc.

Imagine a society without use of violence, without any single "law", but only with contracts, network of dispute mediators and ostracism. Private guards will of course exist too, but they'll be paid only when they are transparent and heavily insured against. And will be used against rare random psychos. In this situation, the "common laws" will come out of negotiated mutual agreements between all the clients of mediators done through mediators. And the punishment for not fulfilling your obligations is ostracism: mediators will work on propagating info about your misbehavior to others, so you cannot participate in economic life until you either prove that you are not as bad, as your stupid mediator (in which case he quickly loses all customers), or follow the suggestion to work out your debt voluntarily. For those who do not want to waste their braincycles there is a simple rule: you can secure any contract where it is possible to prove who did what. If your contract is such that no mediator can prove to others that you failed or succeeded, that no one will protect that contract. Mediators and insurers will of course work together to give you the biggest choice of things you can be insured against, but in exchange you cannot have contracts that violate existing client's operations. E.g. you can secure your factory-building contract, but if some guys around are already protected against the pollution, you have to either pay them, or avoid pollution.

So the "laws" would naturally shape themselves in terms of actual, tangible agreements between particular people. No one could say that he was "born" into all these laws. You would only be born into your family, while the adults in your family have choice to re-negotiate the agreements, move out and back etc. (If no one is re-negotiating at the moment, it's because the current state is optimal and everybody's happy.) And as you grow up, you will be able to negotiate and re-negotiate anything. The only prerequisite is absence of physical violence or effective protection against it.