By far the biggest and most sudden update I've ever had is Dominion, a documentary on animal farming:
https://www.youtube.com/watch?v=LQRAfJyEsko
It's like... I had a whole pile of interconnected beliefs, and if you pulled on one it would snap most of the way back into place after. And Dominion pushed the whole pile over at once.
the word "sapient" doesn't have a clear or agreed upon meaning, so plenty of people would say that babies are sentient
Human babies and cats are sentient but not sapient. Human children and adults, if not severely mentally disabled, are both sentient and sapient. I think this is the standard usage. A common misusage of "sentient" is to use it in the sense of sapient, saying "lizard people are sentient", while meaning "lizard people are sapient" (they are sentient as well, but saying that they are sapient is an additional claim with a different meaning, f... (read more)
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.