Here's some background for you from Bill Whittle, There is more at the link but I'm posting the most pertinent part
http://pajamasmedia.com/ejectejecteject/the rot began to take hold in America due primary to a group called The Frankfurt School. Keep in mind that the Frankfurt school is merely a product of where they appear on this great wheel of history – there have been dozens of civilizations that had their own “Frankfurt schools” in languages now lost to history.
But right after World War One, in Frankfurt, Germany the Institute for Social Research – they wanted to call themselves the “Institute for Marxism” but that was too on the nose – was left wondering why the world communist revolution — predicted as a certainty by Marxist social science – was not leading to the international revolution of the proletariat, the actual common working man.
And they figured out that capitalism – damn it! – was providing enough comfort and material gain, enough of an increase in the working man’s standard of living – that it just simply wasn’t going to happen. Ever.
Now, one kind of person might look at this and say, hooray! People’s lives are getting better – guess we weren’t needed after all.
But not these guys. These guys felt they had to bring heaven to earth.
And so they asked themselves: if the vanguard of the revolution wasn’t going to be the worker, then who would it be? And the answer they came up with was: the dispossessed.
The Neo-Marxist revolution would not attack the capitalist economy – that was too successful. The target of the new Marxist revolution would be the Culture.
Marxist philosophers like Antonia Gramsci, and later, Saul Alinski – personal hero to such present-day fellow travelers as Chris Matthews, Hillary Clinton and, of course, The President of the United States – started to create narratives – stories – about America. This rapidly evolved into a philosophy called “Critical Theory” and the idea of Critical Theory was to attack the dominant culture – that would be us – from all sides, simultaneously.
For instance, Black Americans would be told that their labor built the entire country, while White Americans merely sat back and essentially stole everything. Black slave labor did build the cotton economies of the Southern Confederacy, but the entire Confederacy had less factory capacity than New York City alone.
Nonetheless, many black Americans today have been taught that all of this belongs to them and not the truth, which is that that they were, and are, an integral and essential part of the group effort that built this country together.
Likewise, women are told that we live in an evil patriarchy, where all men are tyrants and potential rapists, determined to keep them in a form of domestic slavery, instead of being their partners and helpmates and husbands and protectors.
Gays are told not that this is one of the most inclusive and forgiving societies in the history of the world, but rather home to knuckle-dragging, murdering Neanderthals – when in plain sight, across the seas, one and a half billion Muslims routinely hang or stone or crush to death innocent people merely because of their sexual practices.
And on and on.
And when you try to argue against this social weapon of theirs, this Narrative, this lie that they tell again and again, well then, prepare for their counter-attack, which is called Political Correctness – the attempt to put the argument out of bounds before it can be had.
They use terms like Hate Speech and Racism. They want to put our arguments and rebuttals out of bounds so that they don’t have to hear them or deal with them. They have to exclude those arguments because if they don’t, those arguments are going to kick their asses and they know it.
And by the way: charges of Racism only work on decent people. You go up to a Klansman or a Nazi and call them a racist, and they say “duh!” Of course they’re racists. They’re proud of being racists. But you go up to someone who is not a racist, a person who finds racism appalling and disgusting, and tell them what they are saying is racism – even when it not only isn’t racism, but is in fact the opposite of racism– well, they’ll shut up. Mission Accomplished.
The objectives of the Frankfurt School, of Gramsci and Alinski in their assault on the culture, were laid out in detail and were very clear: Eliminate not only the voice, but the very idea of reason. Destroy history. Delegitimize shared morality. Medicate instead of discipline children. Promote the idea that problems are so complex that only elitists, experts and academics can discuss, let alone solve them. A later pair of American Marxist philosophers developed what became known as the Cloward-Piven strategy: overwhelm America’s social systems – welfare, health care, immigration, etc. by telling people they were owed things, and by intentionally overwhelming them, cause them to collapse – leaving nothing but smoking wreckage, and no where to turn but to the government.
But above all, for this Frankfurt school strategy to work, it needed to foster resentment, envy, hopelessness and despair.
And it’s been spectacularly successful.