Reading your linked article, it's clear that this was viewed as absolute quackery even back then, and is about as conflict-of-interesty as you can get: commissioned by Louisiana at the height of the Civil War, and proposed by a doctor who served in the Confederate Army [1]. His suggested treatment for Drapetomania was "whipping the devil out of them".
This was proposed a decade before the war started and was reprinted widely in the Southern States. That the North found it ridiculous is a bit like saying that because the Chinese Academy of Sciences says there is no such thing as autism then it's obviously viewed as quackery in the West too.
Are you able to tell us a bit more about the Chinese Academy of Sciences saying there is no such thing as autism? I was curious but cannot find anything about this.
There's none lol. I may have participated in studies as a researcher partially funded by Chinese academy of sciences because we had Chinese collaboration, and some studies involved autism biomarker research.
[1]: https://en.wikipedia.org/wiki/Samuel_A._Cartwright