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.
Sorry, could you clarify? What specifically do you think I’m overconfident about? In other words, what part of this are you saying I could be mistaken about, the likelihood of which mistake I’m underestimating?
Are you suggesting that things are done to animals of which I am unaware, which I would judge to be bad (for some or all of the same reasons why torture of people are bad) if I were aware of them?
Or something else?
EDIT: Ah, apologies, I just noticed on a re-read (was this added via edit after initial posting?) that you asked:
This clarifies the question.
As for the answer, it’s simple enough: sentience (in the classic sense of the term)—a.k.a. “subjective consciousness”, “self-awareness”, etc. Cows, pigs, chickens, sheep… geese… deer… all the critters we normally eat… they don’t have anything like this, very obviously. (There’s no reason why they would, and they show no sign of it. The evidence here is, on the whole, quite one-sided.)
Since the fact that humans are sentient is most of what makes it bad to torture us—indeed, what makes it possible to “torture” us in the first place—the case of animals is clearly disanalogous. (The other things that make it bad to torture humans—having to do with things like social structures, game-theoretic incentives, etc.—apply to food animals even less.)