The term “political correctness” may be new but its foundations are not. For centuries, people of color have been expected to not offend white people—and were jailed, whipped, or murdered if they did. From the mid-19th century through the mid-20th century, African Americans were lynched by white mobs for all sorts of “reasons”...The obvious conclusion is that "political correctness" is the name applied to the idea that "some people [are] owed deferentially considerate treatment[.]"
“Political correctness” only acquired a name when, relatively recently in American history, the idea of treating others respectfully was finally extended to include how white people treat black people, how men treat women, and so on. Prior to that, the idea that some people were owed deferentially considerate treatment—even in its most extreme, vicious incarnations—didn’t need a special term. It was just the way things were.
And, indeed, that's just what it does mean. It means that using language or displaying behavior objected to by the class owed 'deferentially considerate treatment' deserves severe punishment. Fair enough, right? We should object to political correctness as a less-severe incarnation of the same bad idea that undergirded lynchings. I wouldn't have put it that way, but I can see the point: just as not adhering to extreme deference in avoiding offending white women was once grounds for excessively severe punishment, so today...
Of course, she concludes the exact opposite of what logically follows from her setup.
Political correctness is a good thing—the idea that we should treat our fellow human beings with equal respect, despite their race or gender or sexual orientation, and the idea that we might all learn and get better at doing so because of feedback and changing norms.No, the frame you set up was one in which "political correctness" is the heir to not treating people 'with equal respect,' but asserting that some deserve especial deference -- and that severe punishment should fall on members of the disfavored class(es) who violate that deference.
Political correctness is thus bad, not good, for the same reason (but to a vastly lesser degree) that lynching was bad. It is a system of punishing members of disfavored classes for failing to adhere to standards of excessive deference in avoiding giving offense to members of favored classes. The good thing would be not doing that.