Kate Marvel over on Salon has a good article on changing minds and promoting your view. While it is about climate change, the advice she gives could also be used to discuss the idea of the Long Descent and the coming collapse of civilization.
"My dad’s politics are, by his own description, “somewhat to the right of Atilla the Hun.” But even he eventually came around to accept that humans are changing the climate. I’d love to tell you that this is because his daughter is clear, articulate, and persuasive.
But what changed his mind was a famous beacon of morality: the insurance industry. My dad sees himself as a free-market conservative, and the noticeable lack of climate deniers at insurance companies made him take the issue seriously. These companies, after all, have no financial interest to believe in climate change if it’s not happening. A company that ignored climate projections could offer much lower rates to undercut its competitors. None of them do."