Political correctness, like all successful forms of social censorship, tends to go through two phases.
There is a loud phase, where average people are actively confronted about why they can't say those mean things any more. Sanctimonious and humourless scolds, buoyed with righteous indignation, delight in vocally complaining about the oppressiveness of some other other innocuous set of jokes and observations. Most of the populace doesn't have much of a dog in the fight, so just goes with the default position of trying not to offend people, and accedes to the request. A smaller group of contrarian reactionaries fights a rearguard action of ridicule and stubborn insistence on the status quo, but usually knows it's a losing battle. Cthulu swims left, after all, so you may as well get on the right side of history™.
This phase is the part that everyone remembers.
But after that, there's a quiet phase of political correctness too. Once the kulaks have been beaten into obedience and the new list of proscribed words and ideas becomes the reigning orthodoxy, what's left behind is the silence of the things that used to be said but now aren't. It lingers a while, like a bell that's been struck, and then gradually fades to nothing. Once this happens, it's easy to forget that it was ever there. What goes unsaid long enough eventually goes unthought, as Mr Sailer put it.
And the only way to see what's gone is to look at the past, and see what used to be said but now isn't.
In the case of political correctness, since it's a relatively recent phenomenon, you don't even need to go that far in the past.
Movies are a great example of this. It's a useful exercise to consider which classic movies from the past couldn't get made today.
Some ones are kept around in the public consciousness as examples of how wicked we used to be - everyone knows you can't make Birth of a Nation any more, but very few people today would even want to. Other movies are partially excused because of their cinematic value, although it's well understood that nobody should get the wrong idea - Gone With the Wind, for instance (1940, 8.2 out of 10 on IMDB). People still like that movie, but nobody would imagine that the current script, with its copious references to 'darkies' would get through even the first read-through at a studio. But this was made a long time ago, so they should get some credit for their good intentions - it was progressive for refraining from using the word 'nigger' and including the word 'damn', both choices of which proved surprisingly far-sighted. So Gone With the Wind gets a partial pass, like a racist Grandma that people still find lovable as long as you don't get her on the subject of the Japanese or crime in America.
But interestingly enough, there are some modern examples too, that people still think of fondly, but couldn't get made today.
Rain Man, for instance (made in 1988, 8.0 on IMDB), will never ever have a sequel or a reboot. It is inconceivable that you could make it today. The entire premise of the movie is that Dustin Hoffman is an autistic savant, and Tom Cruise is his intolerant brother who needs to transport him across the country in order to get access to an inheritance. The premise of nearly every joke is Dustin Hoffman's odd and innocent behaviour, and Tom Cruise's aggressive, cynical and frustrated ways of dealing with it. (Sample quote, yelled at Dustin Hoffman's head: "You can't tell me that you're not in there somewhere!).
As it turns out, the portrayal of Dustin Hoffman's character is actually rather sympathetic - while a lot of the jokes involve the absurdity of his behaviour, at least part of it is about Tom Cruise being a complete insensitive dick about it all, so the broad message is certainly not that it's hilarious to make fun of autistic people. But that wouldn't stop the autism activists having a fit if it were made today. It wouldn't get greenlit, it wouldn't get seriously discussed, it wouldn't get through the first glance through of a script reader, and because everyone knows this, it wouldn't get written in the first place.
Or take Silence of the Lambs (made in 1991, 8.6 on IMDB). The offending premise here is a little bit more subtle - the serial killer Buffalo Bill, whom the protagonists are hunting, is a man who kills and dismembers women in part because he was frustrated at his inability to become transsexual. That is to say, he wanted to become a woman as a result of childhood abuse (because why else would you want to become a member of the opposite sex if your thinking wasn't deranged for some good reason), but he was denied a sex change operation due to said abusive circumstances. It's taken as a fairly straightforward premise of the movie that the desire to amputate one's genitals and attempt to become a member of the opposite sex was, prima facie, an indication of likely mental illness. Hence it's not surprising that he would wind up killing women as part of his sexual confusion and jealousy.
These days, it's a mark of bigotry to even raise questions about whether transsexuals should be allowed to use women's bathrooms, or compete in womens MMA tournaments.
If the movie were being rewritten today, Buffalo Bill would probably be a killer driven by misogyny, and his evil childhood influences would be rejection by women and too much reading of the manosphere. THAT will make you kill people! Transsexuals are just fine, in fact they're better than that, they're almost a protected group (or will be soon - trust me).
And these are just the changes that have happened in my lifetime.
The changes in the zeitgeist that happened before one's lifetime are far harder to see.
If you really want to see what they are, pick a few random primary sources from Moldbug, cited next to each relevant post.
If conservatism is the democracy of the dead, the only way to find out how they might vote if they could is to actually read what they've written.
Who knows what ideas are going entirely unthought in your head, not for having examined the subject and rejected it, but by simply having never heard it at all.