As a native southerner, I can say with certainty that racism has always been acceptable in the Amer can south. Ir became acceptable in the broader American political system when the American south reacted against the 1964 Civil Rights Act, and white southerns flocked in droves to the Republican Party. Unfortunately, the Republican Party bought into that poison and sold its soul to southern bigotry in a lust for partisan power. It is just becoming more and more evident.
In this country it has been acceptable in some places since the founding of this country.
Still against what founding fathers wanted therefore placed in Constitution.
@Sydland it's more complicated I think. The Declaration of Independence was the ideal, where all men were created equal. The Constitution and Bill of Rights are the compromise to get all the colonies on board. As to how slave owners could justify such inhumanity I don't know but there was no shortage of rationalization of immoral acts then just as now.
These two positions need to be addressed in the next election as being against the Constitution and restricting science, medicine, education plus the need to return regulations on the environment,banking,stock market and even heath care which should be returned to non profit status as it was before Nixon. All of these explained properly could guarantee a domocratic win in the next election but they need to show they affect the common man.