Political correctness is the conscious, designed manipulation of language intended to change the way people speak, write, think, feel, and act, in furtherance of an agenda.
PC is best understood as propaganda, which is how I suggest we approach it. But unlike propaganda, which historically has been used by governments to win favor for a particular campaign or effort, PC is all-encompassing. It seeks nothing less than to mold us into modern versions of Marx's un-alienated society man, freed of all his bourgeois pretensions and humdrum social conventions.
Like all propaganda, PC fundamentally is a lie. It is about refusing to deal with the underlying nature of reality, in fact attempting to alter that reality by legislative and social fiat. A is no longer A.
To quote Hans-Hermann Hoppe:
The masters ... stipulate that aggression, invasion, murder and war are actually self- defense, whereas self-defense is aggression, invasion, murder and war. Freedom is coercion, and coercion is freedom.... Taxes are voluntary payments, and voluntarily paid prices are exploitative taxes. In a PC world, metaphysics is diverted and rerouted. Truth becomes malleable, to serve a bigger purpose determined by our superiors.
- Jeff Deist