In a nutshell I regard political correctness as mainstream leftist politics post-1965.
This marked the tipping point between the left seeking equality of opportunity (meritocracy) and switching to equality of outcomes (egalitarianism),
there was a switch from the left being based on economic policy (especially the belief that the planned command economy was actually more efficient than the market) and a move towards cultural engineering via propaganda and 'consciousness-raising',
the beginning of the left's systematic dishonesty - especially suppression and demonizing of IQ research (IQ had been a leftist baby when the left was were concerned with equality of opportunity and meritocracy),
it when the left began their obsession with the Nazis and eugenics (having pretty much ignored the matter for two decades from 1945),
the beginning of a shift away from being a party representing (and funded by) the proletarian working class/ unions to a rainbow coalition of 'victims' of 'prejudice'; and so on...
Of course PC was continuous with socialism (or liberalism as you call it in the US), and socialism grew from atheist radicalism, that from deism and non-conformist Protestantism/ Puritanism, that from Scholastic Roman Catholicism, and that branched off from the undivided Christian 'Orthodox' Church around AD 1000 -
- so the roots of PC are very deep, being indeed the roots of modernity
(which explains why the modernizing opposition ideologies - such as libertarianism, or moderate Conservatism, or indeed any secular political alliance - cannot stop PC, and why PC will be replaced by a pre-modern, anti-modern ideology) -
...but, despite these roots, it was about 1965 when socialism clearly became fundamentally built on lies (and not merely superficially and tactically dishonest), became cut-off from the real world, and from negative feedback, became focused on process rather than outcomes:
and when transcendental inversion and the subversion of Truth, Beauty and Virtue became not just a plaything of the elite but a mass policy.
Another word for PC would be the New Left.
But political correctness is what the general commonsense public call moral inversion - the subversion of spontaneous human morality and its replacement with the opposite.
And this is distinctive to post-1965 leftism, which is why I use the readily-understandable term PC and try to enlarge its meaning, rather than using a more generic name such as socialism or liberalism - which includes types of 'Old' leftism from the era when socialism was merely a (mistaken) set of organizational means to the achievement of the True, the Beautiful and the Virtuous - as conceptualized by commonsense, by natural law, often by nonconformist Christianity.
The difference between - say - William Morris's utopian socialism of News from Nowhere (roughly, an idealized and secular Medieval communal society of craftsmen and free peasants), and the modern Western inverted world of bureaucratic political correctness motivated by the subversion of all forms of traditional Good, is about as extreme as can be imagined - despite their shared deep roots and tendencies.
Hence the need for a more specific term than socialism/ liberalism.
erived from spontaneous human .