The N word is also used in the community. That does not make it any less offensive.
To quote the article you haven't read:
"Hair texture was one of the many rationalizations of the perceived subhuman status of the African, according to Silvio Torres-Saillant, a professor of humanities at Syracuse University. He says the focus on hair began as Europeans tried to rationalize their dominance and superiority.
"[The argument] was based on the phenotype," said Torres-Saillant. "And that included the skin color, their build, their height, and it especially included their hair."
Those negative associations have endured for centuries.