By nature, man is capitalist. But a primitive and natural form of capitalism. He exploit and kill the others. He wants to survive and then he does everything to his favor. But he cannot survive alone, that is why he needs friends/allies to rule over nature, because nature is stronger than human, and by (trying) killing nature, we are killing ourselves.
The Capitalism is just a solidification of ideas that were present in human mind since the beginning of the ages.
A society cannot be fair (from justice) by being equal (from equality); that is, treating everyone the same way, because fairness is not equality. The equality is reached by the people.
E.g., if I hunt an animal and take its meat, by means of justice it is only mine. Then, I have the rights to give (or not) a piece of that meat to everyone. So, the equality is reached by the people.
Equality is help the others to be (at least) in the minimum and reach the maximum.
Equality is equilibrium, and this balance is by no means extreme, as Rich and Poor.