Once upon a time in the U.S. any white man could slander any black person, or any gay person, anyone from a foreign "sh*thole country", and do so in public. And even if some of the people who heard his remarks found them both stupid and harmful, they rarely would dare to express their contempt.
Now, however, social dynamics have changed, and the people who find these comments stupid and harmful will likely say so, out loud, and to the person spewing the remarks. Which is exactly as it should be, and should have always been.
But the end result of this social change is that the automatic privilege that white people (mostly men) used to enjoy when speaking their minds in public, is gone. And now they are being held accountable for their foolish and harmful slander of others, by those members of the public that find it contemptible. And this public reaction to privileged bigotry has for some odd reason been labeled "political correctness". Which was an odd choice of label, since what it really is, is a new and vocal public scrutiny and criticism of a bigoted status quo.