What is "the PC movement"? "PC" usually has some connotation of sensitivity to racial/gender/ethnic/cultural issues, but I have trouble seeing how that applies

What is "the PC movement"? "PC" usually has some connotation of sensitivity to racial/gender/ethnic/cultural issues, but I have trouble seeing how that applies to the criticism of Perkins' remarks. Indeed, I would have thought that the kind of people who use the term "political correctness" in earnest would identify spurious claims of oppression as an example of the concept.