Based on this fact, I notice that the social-justicy types of today bear some superficial and extremely tenuous resemblance to the pro-slavery types of yesterday. Really makes you think."
I'm sorry but this comes across as total nonsense to me. Any "there are x types of people" stuff always reads as astrology for people with STEM degrees, especially when it's as ill-supported as the types given in this article.
Also the article is pretty ahistorical: being "pro-slavery" was absolutely not the unanimous consensus that we like to pretend it was today. There was widespread opposition to slavery: many viewed it as an obvious moral evil. France banned slavery in 1315, for goodness' sake. People knew it was wrong.
In actual fact, the type of people arguing against abolition were people in a much more similar position to Graham: the Economist famously urged delay with regards to abolition, fearing what freed slaves might get up to. Graham's notion that "actually, I'm much more like the abolitionists than slaveowners because we're both such iconoclasts" is extremely weak and, on its face, a little ridiculous.
(also: does Graham really think he's going against the grain with this stuff? Last I checked, opposition to "cancel culture" and censorship is about as mainstream a position as there is. It would be hard to pick a more "conventionally-minded" opinion than "I think free speech is good")