The point here is that the vast majority of people never chose capitalism, it was forced upon them.
The ability of more people to chose ways of living "involving kindness and cooperation" have been drastically reduced, almost eliminated, by the oppressive regime of capitalism.
This was a calculated result of some people being "thinking creatures" and having amassed power to dominate and exploit the rest of us, not about people acting on "animal desires", nor about people having chosen something.
>>Maybe people killing each other is "natural." <<
Do you think killing people *lawfully* (as described in the article I'm not sure you read) is "natural"?
Isn't "rule of law" supposed to be about rejecting "animal natures"?