I agree with Parenti, that humans do have a nature, its just more varied, malleable, and adaptable, but it still has trends and limits, we still exhibit automatic responses to certain stimulus, and we have statistical predictability in a lot of areas.

The “there is no such thing as human nature” line seems like the anarchist rejection of terms, just because capitalists define their preferred system as “natural”. If you look at most of human history tho, we lived in primitive communist, non-monagamous and non-patriarchal societies, and even in the capitalist and feudal age people still reject private ownership in many areas of their lives.