There certainly is a big difference between being polite and being PC.

IMO:

PC means that if you do not adhere/espouse the "correct" view you are a "bad" person, subject to harassment, discipline or outright firing/suspension. It is enforced by the power of the those who know the "right" point of view.

Politeness is a concern for and respect for the differing views of others, and expressing those views in a manner least likely to insult or offend any more than is strictly necessary. Differing views are tolerated and, the hope and belief is that through polite discussion of differing views, something better may emerge. (I know, this all is very old fashioned, but so am I.)

PC is the opposite of politeness. It reflects a totalalitarian/idealogical view of reality.