So what exactly is human nature? It is difficult to define, but it appears that some things can be said about it.
It would appear to a set of predispositions toward attitudes and behaviors that are included a standard equipment with every person. These predispositions can be reinforced, they can be discouraged, and they can also be slightly molded (but only slightly); but they never can be erased. Many of them are useful, but many of them are not (at least with respect to society as a whole).
So what is a society to do with this constraint? It is to do the best that it can. This will entail compromise and what appears to some to be unfairness. It must set up rules that try to eliminate the worst excesses and move some behaviors into a slightly more productive direction. The rules need to be simple such that they can enforced, either by the law or by social pressure.
Doing what the previous paragraph states is what has brought civilization to this point. But people do not realize this. They believe that human nature is as malleable as they want it to be. Simple thought experiments should be enough to show that this isn’t true (think of toddler’s behavior). Yet they believe otherwise. It is the ultimate conceit.