Political Correctness is cultural Marxism. Its goal is to control language for ideological ends. If you can change what something is called, you change what that thing is. So, by getting people to use a certain word to describe a thing, you alter the essence of the thing itself.
Likewise, if you can eliminate words from the language, you limit the opportunities for dissent against the position you wish to argue. Control of language is the goal of those who would define reality not only for themselves, but for everyone else as well.