Morality and moral codes exist in order to allow human groups to survive in a harsh environment. It works so well, that at this point in time, the environment is threatened by us, most of the time. It is human arrogance which makes us think the purpose of morality is to make us better humans.
Moral codes exist to protect existing status quos more than anything else. IOW moral systems protect existing power systems which tend to fail when conditions change which is not really a definition of fitness. Yes arrogance is extant in individual thinking just as is maximization and proportion estimations are perpetuated forms of statistical error in future estimation. None of them are valid nor serving of fitness nor are they part of natural law.
Everybody doesn't like something, but a personal grudge against the power structure does not constitute an argument. I've never contended that morality is natural law, but it is a natural result of the human brain's reaction to threats to existence. If you think there is a better way, please propose it for consideration.
My statement stills stands and the fact that survival of human groups requires an authority structure, is a result of our survival strategy, not our actual strategy. Morality created the power structure, so why wouldn't a society's code preserve the status quo? Again, what alternative model would be better?
The power structure which puts a police force in existence, allows us to hold our property with some sense of security. That's a status quo that most people want to keep in place. The power structure is the source of building codes and traffic lights. If you want to see what life is like without a power structure, turn off the traffic light at a four way intersection. Suddenly people have to settle petty disputes, in groups of four at a time, while everyone else sits in traffic. It's very inefficient. The only reason such a thing is not a great threat to human society is the fact that one of the first things our power structure did was eliminate all the large predators which once killed and ate distracted humans.
People challenge the strictures of morality all the time. This is always seen when standards of living rise, and threats from the environment are put at bay. We can do that when we're not worried about jaguars.