Perhaps dolphins, but that’s about it. They’re the only other animals that seem to have the capacity for culture and robust theory of mind.
But that’s what I was getting at with my aliens hypothetical. “Robust theory of mind,” is subjective. A sufficiently advanced alien species might not consider us to have robust minds.
Certainly it’s immoral for humans to eat each other — we recognize one another as people. But would it be immoral for these aliens to eat us?
And if we’re going to by the intelligence argument and the restructure argument, should we not eat plants either?
Bentham’s argument (referenced by Cantu) is that a being’s capacity for pain should be the chief consideration. Plants, so far as we can tell, do not feel pain.
A meat free approach isn’t necessarily the best way to do that though.
Neither I nor Cantu was advocating for veganism or even vegetarianism.