If you look on Wikipedia you can find a whole long essay on the origins of the term political correctness, what it is for the Left and for the Right, and its satirical usage. But what I am focusing on as political correctness is what your mother taught you: Be nice, don't make fun of anybody, don't single them out or put them down, be inclusive. If that's what I mean by it, then what do I not mean by it, and what's outside its limits? What's wrong with it? What if people single themselves out?
So, what I think our mothers taught us, at least in the American south, at least back in the 1950s, roughly speaking, is to be nice. If somebody is of a different race, ethnic group, or nationality, don't point it out. Of course, that includes not using epithets or pejoratives. Don't call names. Don't mention people's differences. Fat or thin, short or tall, black or white, Jew or Christian, Catholic or Protestant, Methodist or Presbyterian or Baptist. I didn't include Muslim because in the '50s there weren't any around yet, but you get the pattern.
Although earlier it was not genteel to use certain language, possibly the notion of niceness in particular was part of post-World War II mentality. Grievous ills happened because of differences in WWII, and afterward there was a dominant aura of humility because of that. Then somewhat later we had the Civil Rights movement. In that era, too, the dominant voice of conscience led us to be on the right side of progress--not to repeat or rehearse past wrongs.
Eventually that dominant voice was accused of being an orthodoxy that restricts any criticism of minority groups and permits badmouthing of the majority only. PC/non-PC morphed into Left-Right; talk-show hosts complained that nowadays only white males could be insulted; conservatives howled about the hated rich, and so on. Be nice to the rich and powerful-- "reverse PC," I might call it. But reverse PC misses the point that the rich and powerful are by definition not a downtrodden or maligned minority. It can become an excuse for reactionary thinking--for starters, reverting to the same stereotypes about the minority du jour that had preceded the societal corrective. Resorting to such stereotyping or name-calling is not the antidote to political correctness.
In a still broader sense, "PC" became anything you couldn't say in polite society, hence the erstwhile Bill Maher show Politically Incorrect and its focus on the controversial.
But I want to come back to politically correct as being nice and as what your mother may have taught you. Looking through that lens I am going to limit my focus.
Recently there was little-noticed news from Norway that a lesbian married couple heroically saved some of Anders Breivik's potential victims. Was political correctness the reason those ladies didn't become big news? I don't think so, not in my sense of being nice (and maybe fair and kind, as well), because in that case it was the sensibilities of the majority that might be offended--reverse PC, as I called it above. News outlets killed the story not in order to be nice but because they decided it wouldn't sell to the majority. It didn't conform to the presumed majority narrative, so "let there be darkness" on the subject--thus effectively acting to maintain a cultural blind spot.
When Dennis was teaching Sunday School at the Unitarian church, Jesus was characterized in the prepared literature not as just a Jew but as a "Palestinian Jew." Well, there wasn't a Palestine in Jesus' time. Judea was renamed Palestine by the Roman emperor Hadrian after he suppressed the third Jewish revolt in 135 CE. No, the Philistines were not today's Palestinians. Islam arose in the 7th century CE, and Arab migration followed. But most Unitarians had their origin in the Christian tradition and also are liberals. So calling Jesus a Palestinian Jew may be another example of not offending the sensibilities of the majority--not what I'm referring to as PC in the sense of niceness (and, as I will get to below, maybe fairness and kindness).
So, in my sense, PC emphasizes niceness--not hurting the feelings of those who are different. What's wrong with that is if it stops there--just being nice. I can refrain from using epithets and derogatory names but still maintain the belief in someone's inferiority. Did our mothers want us not to think evil about the other, or did they just want us to be nice? Did they want us to be good or just look good? Let's hope we're evolving toward the former--even if we're not all the way there yet.
Silence alone could imply that what one remains silent about is not good and not to be spoken out loud, in other words, a perpetual "Don't ask, don't tell." I could refrain from calling names, and yet by my silence I could be deciding what gets the light and to what we shall remain blind. By where I permit silence to reign I could be choosing what societal narrative will prevail--and who will benefit as a result and who will bear its brunt. By my silence I myself could be participating in the "tyranny of the majority" while pretending otherwise. So the problem of PC is that it doesn't go far enough. Fairness, goodness, and kindness demand more--openness, inner struggle, honesty, courage. Being nice will get us part of the way there, but don't stop with that.
I want to talk about one more point. What if a member of a certain group does want to be recognized, or to point out one of their own? Something Dennis and I have struggled with is the fact I sometimes want to know if somebody is a Jew--say, some political figure or celebrity. Why in the world would I want to know that? To know who is one of me? Who to be proud of, or, maybe, ashamed of? Dennis wanted to claim his mother told him it wasn't nice to notice such things. I insisted she meant not to notice them for the purpose of putting people down. She was a very kind person and surely she wouldn't have regretted my having a sense of belonging, or maybe being affiliated with someone I could be proud of. Think African Americans and Jackie Robinson. Or the first black winner of the heavyweight title. Surely we shouldn't begrudge that.
But what about when I hear Christians celebrating their tradition in the public sphere? For example, one of my favorite fun fiction authors, Alexander McCall Smith, has begun defending Christian mores in recent books and even gratuitously put the subject of a sermon into one. Sometimes I've had a reaction of distaste, as though right away this is more tyranny of the majority and shouldn't be brought up. But, no--that is not kind or fair. With respect to me, Christianity may be "the majority," but mainstream Christianity--and in fact, faith traditions in general--can be besieged entities these days and in need of defense. Nor is McCall Smith trying to deep-six awareness of other traditions. I remember there was a little discussion in one book of an individual who had converted to Judaism and found a new world opening to him. In another book there was a philosophical society that was described as convening an annual meeting in Tel Aviv. Let him celebrate!