Arguing that something’s okay because it’s a natural behaviour is the naturalistic fallacy. The difference is that other species don’t have any choice over how they live or even the mental capacity to think about the morality of their actions. Humans that are well-off and don’t have medical conditions that clash with veganism do.
I used to agree with the second paragraph, but watching videos of pigs/cows/chickens being slaughtered changed my mind. Imo their prior treatment doesn’t really negate what happens there- and even if it did, I couldn’t use ideal farm conditions as a defense when the vast majority of meat I’ve been eating is raised under less ideal conditions.
(This isn’t calling anyone who eats a burger satan, to be clear. Just trying to say my views in good faith.)