I grew up with pretty racist parents and I never heard of the replacement thing until social media came along. Three cheers for social media, and an extra loud one for Tucker Carlson for finding new ways to perpetuate racism (sigh).
My own personal theory about whites who are afraid of Black people is that it originated long ago. Blacks who were able to survive the Middle Passage and later slavery had to be smarter and stronger than the white people who were trying to control them. So instead of admitting that, whites propagated fake news that Blacks were inferior. This got passed on by generation.
The bs has changed some probably, but it's based on fear. The fear is that Black folks really are superior. Not many whites will admit it, but why be afraid of such a small minority of people if you don't think they can outsmart you and kick your ass on any given day?
The American Slave Coast should be required reading for all kids in public schools, btw.
Great article.