well, TOS was PC for its times. It did bring up lots of issues to the screen though, like the first interracial kiss on TV and black/white issues (wasnt there an episode of aliens that had faces half black half white?).
If you think about it, even the modern Star Treks are not entirely PC. You ever seen a fat starfleet officer? No, they dont fit in the cameras. or a puerto rican crewman? No, they dont wanna work in the future either (

ok ok getting non-PC, sue me! haha).
Matter of fact, go to a star trek event. Here in orlando we had a star trek exposition in the Orlando Science center.. they had their staff in starfleet uniforms, which was really cool. Until the upper management came out of the closets with beer bellys stretching that pajama uniform. That was gross. LOL