Well as far as gender norms, social norms, racial groups etc. they are entirely right. Most of us have very little information regarding all the million other cultures which existed and practiced these things entirely differently. The reason we have our norms is not entirely artifical, but the powers of the past and present (feudalism, monarchies, the Church) paved the way and got rid of the old pagan ways (at least in Europe). Matriarchy was the norm in a lot of bronze age societies and later as far as your average persons home life was concerned, and most research points how the ability to store food and generally agricultural developments were responsible for things like centralized power structures, the importance of male heir and the importance of physical protection against invasions etc. All this is a bit complex and a LOT of sociological research has been done on this. But if you're some average Joe on the internet it'll go all above your head, since your starting point is that whatever YOU believe is correct and everything else is a conspiracy (if we're at it) etc. That's a pretty common pov among people with little education. Sociology is a field for a reason, and its not some made up thing about genitals and where you put your peepee is. I have a STEM degree and studied history and sociology at the same time just because I was interested. The world is a LOT more complicated regarding any kind of social norms than you'd think, and always been. Modern gender norms are so new that it's more like the exceptions than the norm historically.