"Someone once wrote, 'Hell is the impossibility of reason'." - Chris, main character in Oliver Stone's Platoon.
Long before breakdown of social cohesion, infrastructure collapse, wholesale destruction and the like, living in a time and place in which there is no recourse to reason as it applies to interpersonal and institutional interaction, frightens me beyond my ability to examine carefully.
I read something years ago about the horror genre, saying that much of its impact is created by the sheer lack of reason - you can't reason with the monster, you can't placate it, you can't bribe it or cajole it, flatter it or scare it away. It represents the impossibility of avoiding death, so nothing you do will escape it.
That can, and has, become the nature of human societies. The lights can all be on, the Internet can be working, I can have AC in the summer and heat in the winter. But I could be subject to immediate and unavoidable terror, loss, torture, expropriation, death, and even worse, all of that could be visited upon my beloveds, without cause, reason, or excuse. Individuals, groups and institutions could have complete and total control over our lives and can dispose of them for any reason or none, and nothing I can do will escape it or bring about the justice of its eradication or retribution.
Many people in the U.S. belonging to various minority groups face this to one degree or other every day, right now. Those in majority groups who don't see or don't care about that state of affairs believe it will never reach them. But when the fetters truly come off, no one escapes it. The implacable monster out to get us is us, is me, is you, and we all become the zombies consuming ourselves until nothing is left.
That's my bugaboo.