Societies suicide through euphemism
"How to sound good to my fellow humanzees: talk about love, equality, friendship, peace, freedom and happiness."
And if you're smart, keep an assault rifle under the floorboards and get ready for the collapse. All societies die this way; they literally usher themselves into oblivion through pleasant comments made to socialize, which then causes such comments to become demanded as the "norm," and reality demonized.
How does anything die? It stops adapting to reality.
Humans, who can program each other with memes, can simply make reality less preferable than socially-accepted norms like the absolute universals above: peace, love, equality, friendship, freedom, happiness.
They're not plans. They're not even reasonable ends. They're qualities and methods, but we so badly want to fit in that we make them into ends.
Reality doesn't agree, and we begin the fall.