For me, it’s hard to find a justification to go vegan by all Theravada or early Buddhism reasons. Just look at the diverse reasonings here.
But as a human living in this era of time of global warming, with a choice and thus power to be able to go vegan, it’s our human responsibility to do so. My motto is thus to go vegan because you are a human, not because of Buddhism.
That said, look at SuttaCentral
If anyone were to kill animals to serve the monks, it’s bad kamma. If we link this to the modern economic system of buying meat= future killing, it implies that we shouldn’t purposely prepare meat for monks. I think the only case where we are allowed to offer meat to monks is if we were happening to have meat which we intent for ourselves or others at the moment, but a monk came walking by. Having no other food, and wishing to do dana, then that meat is ok to be offered and ok to be eaten by the monk. Or if we happen to come across an animal who died by other causes and just scavenge the meat.
The sutta itself also detailed the attitude of monks when accepting food, not with greed. So monks shouldn’t complain if they are all served vegan food only.
And look at the conditions:
In three cases I say that meat may not be eaten: it’s seen, heard, or suspected. These are three cases in which meat may not be eaten.
In three cases I say that meat may be eaten: it’s not seen, heard, or suspected. These are three cases in which meat may be eaten.
If we want to be very pro vegan here, we can note that these statements may not just apply to the monks, but to lay followers as well, even if not, we can aspire to live up to that standard.
Next is that there is no meat killed for us in the statements. Although it is there in the before and after this passage. So to whom the meat is killed for is not really an escape clause to eat meat if you know it’s not killed for you. Also, factory farming meat is killed for the consumer. As long as you buy and consume meat, you are whom the meat is killed for. You can argue that it’s the faceless masses, but aren’t you part of the faceless masses? Unless you go vegan and not be part of the faceless masses.
So as most of us will not witness or hear an animal to be killed live, most of us had seen videos of factory farming like this: YouTube
So as the statements above didn’t say remote viewing and hearing are not allowed, it should count as having seen and heard. Next link is if we seen and heard other animals being killed, but not this one, does it mean we can eat this one, but not the ones we had seen and heard? The practical answer is: how are you going to keep track? Does it really matter which animals get killed, when you lose your appetite for meat after having reminded yourself of the process of slaughtering?
Last one is suspect, of which knowing is a form of suspect. Having theoretically known that meat comes from animals breed, just to be killed for consumption, that’s all that is to fulfill the suspect. So the only people who are free to eat meat are basically kids who haven’t learn of the cruelty of this world yet. Or those meat we scavenge from animals corpses we happen to stumble upon.
Remember that I am interpreting this in a very pro vegan way, the same text can be used by a very attached meat eater to argue into continuing eating meat.
On devadatta proposing vegetarianism to be compulsory, the Buddha didn’t say the monks cannot be vegans. He made it so that each could choose to uphold it for themselves. In the same spirit, the most vegan promoters can do when speaking of veganism to Buddhists is to strongly encourage Buddhists to go vegan, but stopping shy of making it compulsory. But as I said, it’s not because of you’re a Buddhist you should go vegan, it’s because you’re a human.
Lastly, we also have to come to terms with the philosophical implications of eating meat. Attack on Titans have Giant Titans eating humans only, not other animals, and they are terrifying as hell. All the people there say the world is cruel. And humans fighting back against Titans are who we are rooting for. In veganism terms, it’s animals vs meat eaters, vegan promoters are just the voices for these animals. All the possible hatred and aversion you see from vegan voices are unskillful reactions to the cruelty they witness happen to animals who gets eaten. If we can help to not make ourselves the cause of that cruelty, then why not?
YouTube This movie shows the horror of what we had done to animals is unbearable to be imagined upon humans. As most Buddhists have compassion even for mosquitoes, it’s logical to to want to avoid such cruelty upon animals.