What fact that you know is true but most people aren't ready to accept it?
Understanding and updating beliefs on deeply engrained topics can take enormous efforts, but sometimes it can be so hard that the listener cannot even in principle accept the new reality. The listener is simply not ready, he lacks a vast background of reasoning leading to the new understanding. What fact that you know is true but most people aren't ready to accept it? By "you know is true" I really mean "you are very confident to be true". Feel free to use a dummy account.
For an argument against the sim hypothesis see https://lorenzopieri.com/sim_hypothesis/ or the full article https://philpapers.org/rec/PIETSA-6 (The Simplicity Assumption and Some Implications of the Simulation Argument for our Civilization).
In a nutshell:
0- Suppose by absurd that we are in a simulation.
1- We are equally likely to be in one of the many simulations.
2- The vast majority of simulations are simple [see paper to understand why this is reasonable].
3- Therefore, we are very likely to be in a simple simulation.
4- Therefore, we should not expect to observe much complexity.
5- But we do observe complexity, therefore we are very unlikely to be a simulation.