Can you give an example of a horrifying hypothesis that you would prefer not to know the truth of even if it was in fact true?

No; like you, I want to believe the truth. (Or at least, I want to want to believe the truth. If everyone who professed to seek truth wholeheartedly really did so, the world would be very different. I cannot claim to be wholeheartedly rational; I can only claim that I try, after my fashion.) There are theories that scare me that I do want to believe if and only if they are true---I'd rather not talk about them in this comment.