> Political correctness is not dangerous. It's just boring.
Caveat that this is a story I was told, one which sounded plausible but not something I can confirm.
Racism led some to think that African Americans had lower IQ, and to use that belief as justification for treating everyone in that group worse.
Political correctness said that any IQ test which gave this result must be racist, and should be disregarded.
Meanwhile, as African Americans had less money and therefore lived in poorer areas, they were more likely to live in rooms covered in lead paint, to have water supplied in lead pipes, and to have older vehicles that (I'm not clear on the connection) something something more leaded fuel.
Lead contamination reduces IQ.
If the tests hadn't become a totem in that political contest, change could've come sooner.
At least, assuming the story is true and not just convincing. I'm not even an American.