kaboro: You are hanging to theoretical straws while stubbornly ignoring reality.
Theoretically you would be correct, but reality proves you wrong, as in recent years, the term political correctness has been used exclusively in the sense that was mentioned to you in the begining, and almost never in any of the ways you mentioned above.
In your circles possibly. But it's still easily mentionned by anyone who feel they are disturbing a general consensus on discursive decency and get the dirty look for that. This perceived consensus changes and has been changing with the years, but also heterogeneously within subcultures. Nowadays, after having sounded so cool and so legitimizing, passed from hand to hand, this word is activated a lot in the far right arsenal (along with "triggered", "offended", "snowflake" and all these fallback readymade elements of language), often to shrug off the criticism of genuine abjections. But it is still largely associated with times where progressive humour was transgressive, and where transgression by itself was a breach into conservative conventions, bringing fresh air into uptight norms of decency. That's precisely why it is used so much. It has the comfy aura of a refuge value, gained in a very broad array of contexts. It's a reflex word. People don't even think about its actual meaning(s). "Politically incorrect" doesn't mean anything, it's a scam, but it's actually "politically incorrect" to point it out (see?).
So, mention the pressure of political correctness, and it'll evokes anything and everything, like a Rorschach bolt. It evokes the religious pushback against Life of Brian. It evokes the moral outrage around Clinton/Lewinsky. It evokes the hunt of Polanski. It evokes the Charlie Hebdo and Hara Kiri brand of provocative humanist humour, or, in France, the provocative jokes of Michel 'Coluche' Colucci, the humanitarian clown. It evokes dissent, the shock in front of transgressive humour when it was new, and, in a hypocritical fashion, the ghost outrage in front of today's heirs of those comedians, who try to sound as scandalous as possible (pee, tit, dick, lol) and, in order to exist, push in vain against a non-existing wall, tickling society in its rests of taboos - alas the only thing that still succesfully shocks is genuine inhumanity. But it evokes, indirectly, all the everyday frustrations of ordinary interactions and polite restraints, of which clowns avenge us. People need "political correctness" to breach, and, thus, love to complain about it, abstractly. It's, again, common sense. The notion is here, has to be here, before even having a content.
But when you look at the content, people don't agree. Take the most common, vocal, usage of its notion : the martyrhood of populists, revisionnists, racists, and frantic conspirationists. They are nowadays the first ones to refer to this concept publicly and loudly. Each time a neo-fascist is told to shut up, he brings up a conspiracy of political correctness silencing his big truth, instantly making him such a heroic rebel. Amongst all those ordinary people who, when asked, evoke the old cliché of political correctness (a loaded, necessarily negative word, that you're kind of forced to deplore, as if asked whether "there is too much crime and corruption" or not), how many of them would apply this concept to the criticism of populist demogogues ? This question is completely occulted by the emptiness of the word. "
Oh yes, there is political correctness, this is bad, but... him ? No, that's not about political correctness, he's just insane." Hence, what I pointed out, the largely overlapping complain about "hate speech". People feel there is too much "political correctness", and they feel there is too much "hate speech". They don't apply their idea of "political correctness" to their complaint about "hate speech". Regardless of the fact that said hate speech pundits would define it so.
This alone should illustrate how diverse the meaning, and how vacuous the term. And how futile it is to take a given exemple of "political correctness" and assume the position of the polled categories about it. It should be a straightforward reflex. Distancing oneself from the self-centered projection of meaning. Observing how diverse and contradictory one apparently "shared feeling" can be. Just like making a poll about how people feel about their religious beliefs in society, and discovering that atheists feel cornered by believers just like believers feel cornered by atheists. You may conclude that a majority of people feel like a disdained minority in their beliefs, but you can't use this unprecise statistic as a whole to support the specific exemple of either atheists or believers being omg oppressed. Same thing, again, as passing a law about having to shake hands, justified by how many people complain about "incivility".
Take a random Trump lie, being shot down by fact-checking medias. You genuinely believe that all the people who see "political correctness" as an issue will defend him as soon as Fox and Friends pop out the p.c. victimhood card ? That would be the consequence of a homogeneous understanding of "political correctness". And that would be what Trump fans would like to believe, and to present as reality. And that's how that report was used in this very thread.
It is simply false. And if you don't know any people who (rightly or wrongly) complain about "political correctness" in very different ways than the alt-right, if you believe in such a homogeneity, then it's simply a matter of limited exposure.
But basing the poll's interpretations on an assumption of consensual meaning and content of such a term, that's just very bad sociology (good sociology has devices to avoid this trap). And, of course, that's no ethnology at all (ethnology, by nature, avoids this trap).
At least I hope that the authors are aware of this limitation, take their results for what they are, and don't indulge themselves in abusive extrapolations of that sort.
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Edit :
I conflate a bit two cultures. There would be a lot to say about crude sexual jokes or black humour, when compared between France and the USA. And, as such, about the relations between notions of "puritanism" and "political correctness". One more source of confusion around the usage of this concept and its ranges of application.