Actually, there is only one fair thing for God to do, and that is for God to eternally punish us all.
What you are saying is that instead of punishing all the mass murderers, to be fair, if God chose to set one free, he would be morally obligated to set them all free. But there is no moral basis for that idea when it is God who is the omniscient judge.
Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden. One of you will say to me: “Then why does God still blame us? For who resists his will?” But who are you, O man, to talk back to God? “Shall what is formed say to him who formed it, ‘Why did you make me like this?’ ”Does not the potter have the right to make out of the same lump of clay some pottery for noble purposes and some for common use? (Romans 9:18-21, 1984 NIV)
Punishment is not based on God's desire, it is based on his grace and justice. Every person who has a sinful nature on Judgment Day will be punished. No exceptions.
Jesus died so that everyone who ever lived could choose to yield to God's lordship. Without his death, no one could make that choice. It would have been moral for God not to send his son to earth, but it was not immoral for him to do so. He chose the latter because he desired to save us all so much that he was even willing to die to do so. As a result, the sins of everyone who have ever lived have been forgiven by God—but that is a one-sided action (God's side, not a person's side).
Even though we are forgiven, God is not willing to override anyone's will (and never does). However it is still moral for him to command those that knew him to tell everyone about what he had done and the option they have. That he knew ahead of time what people would choose is irrelevant to the fact that people had (and still have) a choice.
Here we see a person's salvation is dependent upon another human and his own response to it:
But if you do warn the wicked man and he does not turn from his wickedness or from his evil ways, he will die for his sin; but you will have saved yourself. ... But if you do warn the righteous man not to sin and he does not sin, he will surely live because he took warning, and you will have saved yourself.” (Ezekiel 3:19,21, 1984 NIV)
We are shown that it is humans who cause the condemnation of a person in John 3:18, Romans 2:1, and Romans 14:22. We are born without righteousness before God and stand condemned due to the evil nature of our parents and ancestors.
I don't understand what you are referring to, so don't understand what you mean.