It's simply the evolution of English language labels for groups and individuals in order to make them feel better about themselves. It should be CD, common decency.
Of course, like anything else, we take it too far sometimes. Can anyone give me an example of PC gone wild? I can't think of one at the moment.
"To waste, to destroy, our natural resources, to skin and exhaust the land instead of using it so as to increase its usefulness, will result in undermining in the days of our children the very prosperity which we ought by rights to hand down to them."~ Theodore Roosevelt (Message to Congress, Dec. 3, 1907)
Of course it exists. "Political correctness" is simply another term for a form of dogmatism not too much unlike that of religious fundamentalism where certain attitudes are accepted uncritically as the price for conformity.
It's all about the propagation of certain memes with various disincentives acting to restrict original thinking.
"you're better off on Stormfront discussing how evil brown men are taking innocent white flowers." Infinite Chaos