There is a lot of behaviours and quirks that we’re evolved with and which we unequivocally consider being immoral. Like, racism for example.
If your morality includes promoting well-being of others, killing and eating said others, while having perfectly good alternative, goes kinda against it. If you for some reason only include humans (and probably dogs and cats I suppose) in a list of others that you care about, animal farms still contribute so much to our downfall, advocating for not doing it is the only consistent position.
Obviously, it’s not illegal to admit that your morality doesn’t goes beyond the boundaries of your body (or your family, whatever), but I would argue that we kind of need different word for it at this point.