When did affirming human nature become evil?

It probably began with the ancient religious duality favoring the spiritual over the material. This was a theological error: the inward spiritual path to the God or Father Within is only the symbolic-experience of the real Godhood reached through material-supermaterial evolution.

In out time, egalitarianism, internationalism and heterogeneity have taken the place of homogeneity and ethnic differences, under the ubiquitous banner of modern liberalism, which also calls real human nature evil. The political error of modern liberalism represses basic human nature, which remains as it has been for tens of thousands of years, that is, kin-centered, tending to be ethnocentric, even xenophobic, and religious-making, among other things, with group-selection as the primary unit of selection.

Ethnopluralism, which directly affirms real human nature, will rise in contention with modern liberalism.  Liberalism has been exploited by those who rise to power on the denial of human nature.  And various serious abuses of one-race imperialism have helped make the affirmation of real human nature virtually an evil thing, that is, the affirmation of human differences and the protection of diverse ethnic states.

But real human nature is on the side of the ethnopluralism hypothesis, and this will gradually and naturally help it rise. In the United States the separation of powers and states can even accommodate such an ethnopluralism, which could eventually save the nation from civil and ethnic strife.