The way I see is that it's basically shit but in a different package. If both the un-PC and PC terms mean the same thing, then how is the PC term any less offensive? Just because it's worded differently?
Also, the current "PC" words will eventually be un-PC. Idiot, spastic and retard were PC terms back in the day for example.
I think the key concept of PC is same concept of framing used in propaganda. It's rewording a term or statement into a more positive agreeable meaning, but while at the same time, still retains it's real negative disagreeable meaning underneath. Although in most cases as you say, such framing will expire when people start associating those terms as an negative once again. I can't wait for the day when "Special" is used as an insult lol, oh wait, it already is sort of, "Oh so you think you're so special eh?" Quick PC faggots, come up with a less offensive term pronto!
With all the serious issues in the world, why is regulating speech such a high priority? We've fucking up Earth, on verge of a new world war, becoming idiots due to technology replacing all our mental abilities; but OMFG! We must keep our words/terms/statement proper! I honestly don't get it.
By the way, what is the PC term for midget these days? It is vertically challenged?