I am unsure if 'political correctness' was ever used non-ironically. It certainly hasn't been so for a very long time. Usually it is used as an attack.
Personally I translate it to 'good manners'.
Personally I translate it to 'good manners'.
I suppose there is some chance that they are being slightly more sophisticated and making the argument that the expectations are strictly performative. But I doubt it.
The use of political correct terms makes people mad because it contains within it an implication that they are being rude, and often the person coming up with these euphemisms has not the faintest idea whether the existing term was offensive or not!
But as an atheist of Jewish descent, what do I say to my co-workers, who are from Turkey, India, Korea and China? Of those who I know to follow a religion, none are Christian. It would feel outright silly to say "Merry Christmas".
(For comparison, try saying "Happy Hanukkah" to your non-Jewish friends as a non-Jewish person when the season comes, and see if it makes much sense to you).
My question is more whether you care if someone you don't know says it to you on the street or when you buy a coffee or whatever.
On the other hand, different people are rubbed the wrong way by many different things. I do try to avoid going out of my way to avoid offending people, by, say, assuming they're Christians. And on the other, other hand, I'm fine with offending people who want to go out of their way to be offended.
That's probably true, given that "happy holidays" predates "political correctness" by more than a few decades.
I know that the term "barrierefrei" is PC, and I know that quite a lot of people will hate it for that reason alone. I use it nevertheless, because I think that PC terminology is actually a good thing (to be used, not to be enforced), and that "barrierefrei" is an especially well-chosen term.