Murder is wrong because its unfair to want to live and to take another persons life who wants to live. You are taking advantage if you do this. So it is unfair. Punishing a person who has committed murder is obviously fair if you know what punishment they deserve which we do not. Every society has a different opinion for what the proper punishment of any crime is. Thats half of right and wrong that we dont have figured out. Knowing what someone deserves is an important part of morality and to say you dont know what someone deserves would be a lot better than just throwing a number out there like the law does with its three strikes rule and its entire sentencing for that matter. Three strikes and your out is a baseball rule. What are the chances that three strikes is the proper amount of leniency? Someone just liked baseball had no clue how many strikes a person should be afforded and through that number out there even though this is probably more than some people deserve and less than some people deserve as our brains are very much different from each others. To know what someone deserves you would have to be them and we cannot do that. Even if you knew what someone had been through and how they feel and think you wouldnt know exactly what they deserve. If you think fairness has nothing to do with right and wrong then i invite you to show me one thing that is wrong and fair or right and unfair. Our views are shifting more and more to what is fair though none of us know it. Its the only thing that makes me think our leaders may not be that bad but all the other evidence suggests otherwise. If you want more examples read the following. It is wrong to steal a car because someone worked hard for it while you just took it. Think about a game. All game rules are based on what is fair. To give all opponents and equal shot at winning. Well in life we have rules at least in this day and age to give everyone an equal shot at succeeding. So if you steal a car your taking an advantage. That is why it is wrong. If that isnt why it is wrong then tell me why it is wrong and i bet you cannot come up with any objective premises for stealing being wrong.
Why? Because the whole "fair or not fair" thing is already subjective. It really depends on a person's point of view. For example, imagine a guy with a inborn talent, say a very high IQ. He has to compete with another, ordinary children in a Puzzles. Should both boys be given equal time to solve the puzzles to make the game fair? Or should the ordinary boy be given extra time for the high IQ boy has a massive natural advantage? Obviously, whether a decision is fair or not here relies on each person's view point. And because we cannot even decide objectively and methodically what is fair and unfair, right and wrong would be subjective as well.