I don’t remember where I was, what I was doing or even when it was that I first heard this expression, but I remember like yesterday my reaction and that reaction was fear. That something could be declared correct or incorrect due to the politics of the moment or what the socially and politically dominant train of thought is at any given time is something that chill to the bone anyone of anyone who cherishes the rights guaranteed to us under the First Amendment.
It might be easy to dismiss PC as just more silliness in the world of what currently passes for political discourse, but we take it lightly at our peril. Early on its proponents seem largely concerned with redefining some words deemed as pejorative when used to describe certain groups of people. Whether or not it changed or improved the status of said groups was irrelevant, the offending term had to be changed.
Most of this seemed somewhere between needlessly disruptive and just plain silly but ultimately harmless enough. But the real target of PC was, is and always will be offensive words but rather objectionable ideas. That the term was used by both Trotsky and Goebbels should tell you all you need to know about the ultimate goal of absolute control of information.