What is one of the scariest things to a human? What is one thing you can suggest to them that can make their hair stand on end, or shut them down, or get downright violent?
The world that you believe you live in, is not the only way to view the world.
This goes deeper than you probably realize. Save perhaps for a few spiritually enlightened people every human on earth is firmly and unknowingly addicted to their own perspective of the world being the one true reality. At the same time, a percentage of these people will evolve their psyche and outlook on the world over the course of their lives. Sadly, a larger percentage of these people will live their entire lives addicted to the same reality, whether by environmental factors, or just pure stubbornness.