I think PC is a generally good idea, the execution of which has unfortunately been taken far too often past the point of absurdity.
I do believe that the initial or underlying purpose was well-meaning and appropriate, meant to halt the blatant rudeness of people going around saying "******" and "crip" and "retard". I don't think there are many people who couldn't benefit from a reminder to be more culturally, politically or socially sensitive.
However, humor columnist Cynthia Heimel, who is a staunch liberal, wrote a very funny piece some years ago about how PC-ness has basically become a parody of itself. She cited a party where she was informed that it was not PC to say, "My God, it's nippy in here, I need a sweater" because it was deemed to be offensive to Japanese-Americans.
She also recalled a talk show she was invited to co-host with comedian Mo Gaffney, where the topic was friendships between gay men and straight women. During a commercial break, Heimel said to one of the men, "Hey, nice socks. Oh, but they would be, you're gay." All 4 guests glared at her and accused her of "perpetuating gross generalizations." Mind you, she was brought on the show for the sole purpose of being funny.
See, I think that's the real problem right there. Nobody has a sense of humor anymore.
(Edited for redundant redundancy.)