Let's start with an uncontroversial statement. Animals suffer. While exactly how different species feel pain is debated, most of the animals we eat clearly suffer in ways that are morally comparable to our own. Secondly, outside of those with very specific dietary requirements (a minute subset of the population) the majority of Homo Sapiens can obtain all their nutritional requirements from a plant and dairy-based diet.
If you accept both these prior statements, you then have to confront the fact that the majority of meat is produced in a way that causes large amounts of unnecessary suffering. Confinement, mutilation, social isolation, forced impregnation, and premature death. These methods are used to facilitate the cheap mass-production of meat at scale.
These statements normally incur the following objections:
1. Human beings are natural omnivores, therefore eating meat is morally fine
A natural behaviour does not imply morality. It is natural for me based on first principles to 'come at you bro' if you sleep with my partner, to hoard resources to improve my survival chances, or to die of preventable disease. Our ancestors did many things out of necessity, lack of alternatives, and knowledge. The modern Western world does not slaughter animals because we would starve without doing so. We do it because it's affordable, convenient, and abundant.
2. One person eating meat doesn't make a difference, so my choices are irrelevant
This same argument justifies littering, tax avoidance, and not voting.
Supply chains respond to aggregate demand. Reducing consumption by even a small amount reduces the number of animals bred and killed. The world being large does not magic away causal responsibility.
This argument also undermines any grounding for individual morality. If 'my impact is tiny' excused harmful actions, then every avoidable harm becomes morally free. You could spit on strangers in the street as long as the total number of spits (apparently this is the plural of spit) delivered by the human species this year is dominated by someone with a genetically engineered super-soaker strapped between their teeth.
The uncomfortable truth is that individual choices matter, because they exist within a system that reacts to them.
3. Better a short and mostly pleasant life ending in a quick death, than no life at all
If the creation of a being is morally justified as long as we give it some pleasant early experiences, then we have justified some inhumane actions. We can breed humans to harvest their organs, so long as their childhoods were full of laughter and League of Legends (clearly a joke, this is a fate worse than genital mutilation).
The deeper problem is that the better to exist than not exist is conceptually incoherent. Non-existence is not a state in which we can harm others. There exists only the world as is, and the moral question of what you choose to inflict on the individuals who exist within it. Once an animal is born, it has wants: avoiding pain, continuing to live, maximising pleasure. Killing it, even painlessly, removes all future good experiences it would otherwise have had.
4. Large numbers of insects will instead have to die for the switch to a plant-based diet
I don't buy this argument either. Raising animals is already incredibly inefficient. To produce 1:
- 1 calorie of chicken, you need ~9 calories of feed
- 1 calorie of pork, ~15 calories of feed
- 1 calorie of beef, ~25 calories of feed
Every extra unit of feed is extra land, extra fertiliser, extra pesticides. 26% of the Earth's surface is devoted to grazing land, while 33% of all arable land is used to grow feed for animals1. You are not avoiding insect deaths by eating animals - you are sandwiching the animal in the middle.
5. Dairy farming is still immoral
Yes. Dairy farming involves its own set of grim realities: forced impregnation, the removal of calves from their mothers (often within hours), and eventual slaughter once its yields falter. However, this does not salvage meat-eating from scrutiny. Pointing at a second moral failure does not retroactively sanitise the first. If anything, the dairy objection strengthens the case for reducing animal products altogether. Reducing suffering is better than sustaining maximal harm because perfection is difficult. Abandoning meat does not end animal exploitation, but it's a step towards removing one of the larger sources of suffering in our world today.