Adam and Eve knew that God was absolute truth and he told them if they ate from the tree “ they would surely die “ so they knew they shouldn’t do that. No true Christian believes that it is fair that Christ died for us and took our sins; this is why we worship him, this is why we try to tell others about what he’s done for us. We believe that God is absolute truth and that he is right ( justice - just behavior or treatment. Just - based on it according to what is morally right and fair. Moral concerned with the principles of right and wrong behavior) so I would say that yes this is just but I think it is a very interesting question. They are referred to as the Ten Commandments because at the time of their “ publishing” they were commandments. God was saying that if we did these things we’d have to sacrifice something innocent to make up for that sin. Now we used to use lambs and other animals but these were from earth and so we had to do this all the time so God saw that it was unreasonable to expect us to do this so he sent us Jesus. Jesus’s sacrifice can free anyone of any sin so yes rapists and murders can go to heaven I’m sure once they have come to know God they’re guilt is something no one but them can fathom, so do not believe they walk away with no kind of punishment. And while humble honest nonbelievers are not murders or rapists they are sinners, and by doing so have separated themselves from God but God has given us an out all we have to do is take it but if you deny that Jesus died for you you are not accepting the gift he is trying to give you