I was an undergraduate at UC Berkeley during the heydey of political correctness. Everyone in the dorms was urged to attend DARE seminars - not "Drug Abuse Resistance Education" but "Diversity Awareness Through Resources and Education." The goal, quite plainly, was to create a one-sided educational culture so the next generation would accept the self-styled awareness raisers' agenda as gospel. Political correctness isn't just hypersensitivity; it's hypersensitivity designed to place a permanent stamp on impressionable young minds.
From this perspective, political correctness isn't essentially leftist. Indeed, with the benefit of hindsight, leftist political correctness hasn't been all that effective. The full-blown triumph of political correctness, of hypersensitivity plus one-sided education, is patriotism.
Not so long ago, as Eugen Weber observes, most people were only dimly aware of what nation they "belonged" to. They took little offense at insults to their country, its people, or their flag, because they just didn't much identify with their country, its people, or their flag. Then came the patriots, descending upon their nations' schools like locusts. They taught children a litany of bizarre nonsense. They urged them to love millions of complete strangers who happened to live inside a Magic Line (a.k.a. "the border"), and loathe those who snickered during the Pledge of Allegiance or improperly folded the flag.
And despite the justified indifference and puzzlement of older generations, the patriots won. There's no need to speculate about what a politically correct world would look like. We're already in one.