Animistic cultures feel may feel empathy for sacred objects, like boulders or trees, or dead ancestors, or even imaginary deities with no physical form.

Ya.. I'm not buying this here - that's a giant false equivalency. You're comparing inanimate objects to conscious beings; you're also comparing religion and spiritual cultures to scientific arguments.

Where do we draw that line? Is it only a matter of degree, not kind? How much uncertainty do we tolerate before changing the category? If you take the precautionary principle, so that something is morally important if there's even a small chance it could be, aren't you the same as the rock worshipers neglecting their fellow humans?

I'm not saying this is black and white, but its not nearly as gray as you're making it out to be. You can pick solid, semi-non arbitrary places to put the line. To start, biocentricity is never actually followed; no one cares about bacteria. Anthromocentricity is based on a marginal cases argument and speciesism. Sentiocentricity is based on the fact that these other beings feel things like ourselves and experience the world subjectively. That's why I pick sentiocentricity. Sentient beings can suffer, and I inherently think suffering is wrong. If you don't think suffering is wrong, there's nothing to say here.

Why do you believe animals can suffer? No, we can't take this as a settled axiom. Many people do not believe this. But I'll try to steelman. My thoughts are that generally humans can suffer. Humans are a type of animal, thus there exists a type of animal that can suffer. We are related to other species in almost exactly the same sense that we are related to our grandparents (and thereby our cousins), just more generations back. Perhaps whatever makes us morally relevant evolved before we were human, or even appeared more than once through convergent evolution. Not every organism need have this. You are related to vegetables in the evolutionary sense. That's why they're biochemically similar enough to ourselves that we can eat them. You're willing to eat vegetables, so mere relation isn't enough for moral weight.

http://fcmconference.org/img/CambridgeDeclarationOnConsciousness.pdf

You're really bringing up the plant argument? Even if plants were morally considerable, which they aren't because they can't suffer, it would be more altruistic to eat plants because of the way trophic levels work.

Consider the Mimosa pudica, a plant that recoils to touch. Is it morally acceptable to farm and kill such a plant? That's just an obvious case.

Aversive behaviors is not indicative of suffering. Plants don't even have a central nervous system.

But again, you're fine with eating plants.

You say I'm fine with eating plants, as if this isn't a problem to you. If you care so much about plants, become a jain.

I think it is a near certainty that the simplest of animals

Based off what evidence? I'm not saying something either way for animals like jellyfish, but you can't just say "near-certain" with no backing.

I also think there's a significant chance that animals as advanced as gorillas are not conscious in any morally relevant way.

Where are you getting this? You have nothing backing this. You can say you think this, but you can't randomly say there's a "significant chance."

I am morally opposed to farming and eating animals that can pass the mirror test.

See, this gets more nuanced than you probably originally thought. When it comes to the mirror test, its not as a black and white as you may think. Not all animals use sight as their primary sense. Just learning this piece of information calls for a revamp of the test; its not as if this test was the most fool proof to begin with. I bring this up because dogs were recently found to be self-aware based on smell rather than sight; dogs primarily use sound and smell. Many other animals use other senses.

https://en.wikipedia.org/wiki/Mirror_test

Look at criticisms of the test^

What about humans too young to pass the mirror test? Is it morally acceptable to kill them?

That's a question you gotta ask for your own moral framework. You're the one wanting to kill non-self aware beings.

Are vegans as a subculture generally pro life, or pro choice?

This is irrelevant. Most vegans are pro choice because pro life is based on very little actual evidence while pro life is.

Lower animals may have some analogue to our pain response, but that doesn't mean it hurts.

What does lower animals mean? And sure it does, mammals and birds are conscious so it isn't just a pain response. It isn't just noiception.

If a wild animal attacks your human friend, you shoot it dead. If a dog attacks you while you're unarmed you pin it to the ground and gouge out its brains through its eye socket before it rips your guts out. It's the right thing to do.

Rhetorical appeal haha?

if you had a pet cat, would you feed it a vegan diet? Even though it's an obligate carnivore, and would probably suffer terribly from malnutrition? Do carnivores get a pass? Do carnivores have a right to exist? Is it okay to eat them instead? Is it wrong to keep pets? Only if they're carnivores? Why such prejudice against omnivores, like humans? Meat is also a natural part of our diet. Despite your biased vegan friends telling you that meat is unhealthy, it's not. Most humans struggle getting adequate nutrition as it is. A strict prohibition on animal products makes that worse.

I have answers for all of these, but you asked so many loaded questions. I don't have a pet cat, but if I did, I would preferable feed said cat lab meat. Do carnivores get a pass? They don't get a pass, but for now they do require meat. I'm in favor of minimizing wild animal suffering and there are different strategies for that, being genetic engineering, lab meat for carnivores, etc. This is too far in the future because we don't have control of the biosphere, so the environment will have to do for now. Is it wrong to keep pets? No, as long as they aren't treated as property and so they are treated as family. Meat is also a natural part of our diet? Wait, so something being natural makes it right? Nope. Despite your biased vegan friends telling you that meat is unhealthy, it's not. Thanks for being condescending, but no I've done the research myself. It can be more healthy. High doses of processed meat is unhealthy; I can link sources.

But maybe you think farm animals are more innocent than indifferent. They're more domesticated. Not to mention herbivores. Cows have certainly been know to kill humans though. Pigs even kill human children. Maybe cows are not very nice people.

This is low, especially for a rationalists. We both know that had nothing to do with anything and was only a rhetorical appeal. Its not like many humans are nice people: murder, wars, etc etc.

All I'm seeing here is a whole ton of sophisticated arguing and a whole lack of actual knowledge on the subject. You wrongly assume that vegans are hippies who act on their feelings and there's no factual basis behind it. You sure its not that you just really want to keep eating your tasty bacon and steak?

You say you're against killing self aware beings. If pigs were proven to be self aware, would you quit eating them?