Plants, as mentioned elsewhere in this thread, are also capable of nociception. In advance of further discussion, my preliminary conclusion is that the vegan line is just as arbitrary as any other, but drawn so as to more tightly circumscribe those species on which the infliction of pain is acceptable, presumably out of a desire to inflict the least possible harm -- an honorable intent, but I think not honorable enough to satisfy at least some vegans, who insist upon seeing themselves as taking the only moral option, rather than merely the least practicable immoral option.

(I have to admit I don't really understand any of this dietary hair-splitting from the inside. My species has gone to a lot of effort in becoming this planet's undisputed apex predator, and as far as I'm concerned, I may as well get the benefit.)

We aren't the apex predator. Yes, we do have everything necessary to kill any one animal on Earth and eat it. Even animals that are usually poisonous, like the pufferfish, the fishing of which is strictly regulated because otherwise we'll eat them all.

On the other hand, we're not actually eating all the species. Most of us are almost exclusively eating species that through the miracle of selective breeding have been bred to be delicious, nutritious and easy to kill.

We stopped trying to satisfy our dietary needs by way of becoming the apex predator once we figured out domestication.

"Apex predator" doesn't mean "eats everything", but rather "eats what it please and has no predators of its own". By that standard, we're the most spectacularly successful predatory species this planet has yet seen, to the extent that many of us never have to hunt even once in our entire lives.

Plants are not capable of nociception, as far as I can tell from my familiarity with the biology. They don't have nociceptors. They don't have integrating organs to interface with nociceptors. They don't feel.

I'd be happy to have you explain how this is not the case.