I try to be careful with the phrase "political correctness," because used as a term of criticism, it's tossed around as an excuse for disregarding culture, diplomacy, perspective, bias, empathy, etc. Everyone who's lived or traveled much internationally knows that their own culture and subculture is just one of many. After experiencing the international revelation, you know that it would be foolish to completely disregard the cultures and customs of others, just as you would think those others would be foolish at best if they completely disregarded yours.
The revelation, if you do experience it, brings two seemingly opposite shifts. First, you are less sensitive to insult. You realize that cultures, customs, standards, manners, styles, displays of emotion, body language, personal space, dialects, and other practices differ. You assess from a broader view. You're more aware of your own cultural expectations and where they stand in relation to others, and you see that you could have grown up with any other expectation simply by being born in a different place or time, or even just in a different family. Your understanding and tolerance expand.
The second is that your sensitivity also expands. By this I mean sensitivity toward others. You understand that what does not upset you, or perhaps even anyone you know, could upset someone else, and this someone else could still be perfectly reasonable and decent.
People who grow up in abusive circumstances often suffer the opposite forces. They become less sensitive to the upsets of others (after all, they may have experienced and gotten used to worse, or may have learned to grow up in self-preservation mode, focusing less on saving others they cannot save, just trying to stay alive). And they become more sensitive to possible disregard, rejection, insults, mockery, or abuse toward themselves. The combination tends to give many new potential friends a very bad impression, even quite quickly after meeting the person. But it's quite a predictable result of childhood abuse.
The next time you see someone with this kind of double standard, keep in mind that it's probably mostly or completely invisible to them, and also probably not simple to correct even if pointed out to them directly.
What I will call "hypercorrectness" can show up in regard to others or to the self. That is, someone can become overly concerned about minor details even to the point of their "correctness" becoming totally incorrect - either when it comes to how others are treated, to how they themselves are treated, or both.
"Hypercorrectness" is usually a language phase young children go through. That's its typical meaning. For example, when I was little, I had noticed that you add "-ed" to make actions past-tense. So I argued intensely that "went" wasn't a real word, and "goed" was right because it took "go" and added "ed." This was both amusing and annoying to my mother, and she's often told the story - and I remember it clearly, in fact. But it's a classic mistake children will make. They will learn a rule, then overapply it, thinking it's more regular, universal, and infallible than it really is. That's hypercorrectness.
I've worked for many years as a tutor, most of those years in centers that are very diverse. I'm white. And European by family and country of birth. Most of the students I have taught, though, have been peoples from all around the world. And relevant to this next point, in a center where I worked for three years, more than half of the students were black. One thing I noticed occasionally was that two, three, or four students would be talking, and I would hear the word "white," and then I would hear "SHHHH!! Don't be a RACIST!!!" and then laughter and other comments. Some of them might look over at me. This was not something I minded one way or another, and it amused me, and I guess it was nice to feel like people were concerned about not offending. But it's hypercorrectness. There's nothing actually wrong with saying the word "white" or the word "black" in reference to a person. Black people typically call themselves black. No, they are not literally black of skin. But that's what people say, and they say too. And I also call myself white without mulling it over or thinking there's something wrong with that, even though I am not literally white of skin. But then someone who is different from you is in the room, and you don't want to refer to them in a way they don't like - or, necessarily, call attention to the difference. So you may well be on your best behavior and try to be extra careful not to say the wrong thing. Hence hypercorrectness of this kind.
Another time, a black student pretended he had forgotten the race of someone who was openly racist toward his family in a true story he was writing. He started to say white, then interrupted himself and said he didn't remember. He didn't want to offend me or make the wrong implication, which I immediately understood. It was an uncomfortable story, but it would not be racist of him to identify the racist as white while telling the story to a white person. But I totally empathize with his situation in that moment. I was uncomfortable about the story, and it was just a piece he was writing - making me personally uncomfortable wasn't what he was going for. But it was a good story to tell, and it had really stuck with him for a reason.
Hypercorrectness can be perceived as biased or racist. For example, in a study in which participants were asked to direct someone to one of several photos by describing it, the participants who avoided using charged words like "black" (when that would have made things easier) were seen as more biased/racist than people who used outright racial slurs. That's kind of extreme! Sometimes it's the things you don't say, right? But it goes to show that correctness and hypercorrectness are not exactly simple. And in some cases that inference will be correct. If someone considers "black" a dirty word - enough to avoid it when it would be really useful - that might mean they consider people of color to be somehow bad in general. Another circumstance, though, is that they do not want to offend or draw attention to a contentious difference or point of pain. They are simply anxious or bending over backwards to be accommodating (and perhaps not doing so quite right, but it's the thought that counts).
This topic is too complicated to brush aside with one hand and one contemptuous reference to "political correctness." There's nothing wrong with correctness. Correctness is good. And hypercorrectness is actually quite understandable. Often it means well.
Understanding usually means respecting. But sometimes even if you don't understand, respect will be important. Whether "political correctness" is the sensitive, useful, diplomatic, realistic kind or the hypercorrect kind, is it very hard to understand?