The article reads more like a left leaning op ed than an objective encyclopedic article. A good example is this unsourced assertion early in the article:
"By the early 1990s, the term was adopted by US conservatives as a pejorative term for all manner of attempts to promote multiculturalism and identity politics, particularly, attempts to introduce new terms that sought to leave behind discriminatory baggage attached to older ones, and conversely, to try to make older ones taboo."

US conservatives didn't "adopt" the term in the early 90s; it would be more accurate to say that by the early 90s the excesses of "political correctness" became more widely known and many people (not just "US conservatives") began to ridicule it (particularly as manifest in the implemnetation of draconian speech codes on college campuses and the aggressive promotion of increasingly dubious and absurd assertions of what might be construed as "offensive"). The term has come to be used in mischevous ways at times by people to ridicule positions they disagree with (an example would be creationsts categorizing the teaching of evolution as "political correctness"). 

The article in short seems to reflect the perspective of someone of an "activist left" sensibility that is more interested in addressing popular backlash against political correctness than in objectively describing it. It's really not as complicated as the article makes it out to be. In brief, politically correctness is simply a word for efforts to alter or prohibit innocuous language or other activities that are unreasonably or implausibly asserted to be offensive. Unfortunately efforts to honestly describe it seem to be a magnet for what might be called "political correctness denialists" (the idea that there is no such thing as political correctness; it's all just right wing agitprop etc.).