Kant started it. He said things are not when they seem to be. Hegel played along, saying "The Truth is the Whole", one must accept both A and not A to know truth, and how the view of the majority is the truth. Marx picked it up. Then after Socialism failed, Post-Modernism became necessary, and now we have neo-communists like Zizek parading it.
What they say in essence is still the same thing Kant started:
- Things are not what they seem to be.
- Freedom is slavery.
- War is peace.
- You can have your own cake, and let your neighbor eat it too.
- A is not-A.
But if they say that out loud, no one would accept it.