This is gish-galloping, to properly address your points, every paragraph would require 3ish paragraphs, so I’d have to spend the better part of 2 hours responding, which is totally unreasonable to expect in a forum like this with a stranger you have no personal attachment to.
From what I gather, your main issues are social ostracization and false equivalencies. Using social norms to drive your moral decisions is obviously problematic, you can think of a ton of atrocities committed by humans when those atrocities were socially normalized. People aren’t born evil, with an intent to cause harm. They’re taught to be ambivalent, and can perpetuate atrocities through apathy.
As for the idea that there’s some false equivalence, you’re misunderstanding the thought experiment. Yes, eating humans is more dangerous than eating chickens or dogs, but that’s a happenstance of nature. It’s possible we could figure out a way to eliminate prion diseases and other harmful effects of cannibalism, and then farming disabled humans who process information at the same level of a cow would be morally permissible to a logically consistent non-vegan.
Of course, essentially no carnists are logically consistent. They use emotion and preference towards certain species to guide their decision instead of rationally considering when it’s okay to harm something (taste pleasure isn’t a high enough bar to inflict pain and death, obviously).