There are some excellent arguments and analyses in the "Human Rights" thread for a way of formulating a rational set of human rights.
But basically this: You have the right to life. If you recognize your right to life, then you must recognize other people's right to life. Any action you perform that infringes upon the right to life of others (unless they do so before you) should be punishable by law. Any action you do that does not: (making porno videos of yourself, kinky sex, homosexuality, eating unhealthy foods, swearing a blue streak) should not be. Arbitrarily removing the freedom of choice which allows a person to live their life is immoral.
Granted, this leaves some leeway in interpretation, but viewed this way, it becomes apparent which historical laws are unjust.
The only time you see friction due to inclusive laws (laws which do not force people to conform, but which are truly inclusive and allow people to do what they want) are when some group objects because they want everyone else to do things their way and their way only.
You don't have the right to live, rights are created by the state which regulates how to coexist with others. To say that you are free to do as long as you follow your rights is a contradiction. You aren't really free if you give up a bit of freedom for the sake of "safety".
And saying that historical laws where unjust, why did they become unjust? Back in the day, there was nothing wrong in believing that it's okay to have slaves or killing indians and the inquisition. Now we seem to be reasonable to say, "That is wrong". Well let's push it. What about abortion, drugs, and death row? There are many examples where logic just justifies what is right or wrong, but not that it is right or wrong. That is my issue with those things. Maybe for controlling the masses, making laws based upon logic may be the right thing to do, but for the more controversial stuff I don't think logic can tell you. It becomes subjective in these extreme cases.
TheDrummingKINGWhat? Encyclopedia isn't saying base logic on laws, he is saying to create laws using logic. Basing laws on religion (which has been done in the states multiple times) seems to me the more "convenient" thing to do (but also the wrong thing to do).
If you don't understand how just and moral laws could come about from logic, then the human rights thread is a good place to read.
I think I might've said it wrongly, but logic doesn't say much if anything about what is moral. This is the issue that Aristotle noticed when doing the right thing means breaking a law that on principle is reasonable. I understand that laws should be based upon logic. But is it sufficient? Doing the right thing can be and not be reasonable. It really depends on the situation, and even then one cannot know if it was the right thing to do. Only in reflection, after the act. it makes sense what was at cost. But you might need a bit of wisdom to know what happened. XoravaX made that point clearly of the issues at stake. Socrates was right, "I know nothing".
If reason killed God, then I can assure you, they also killed justice. If you say it's logical for x, y and z and that makes it moral, No no no, you feel it is right based upon logic. And for the most part it works on common everyday stuff, I don't deny that. But for justice to exist, it is based upon feelings, which it then becomes subjective. When it is not clear whether the choices are right or wrong, then you realize, "I know that I know nothing".