Eating meat benefits more people, counting all the byproducts used in medicine and clothing
A utilitarian count has to include the animals, and tens of billions of them are killed each year for this. It also has to compare meat with the realistic alternative, not with nothing. Most byproducts have substitutes, and the few that don't are a reason to keep using them, not to keep eating meat.
Animal farming does not only feed people. Every slaughtered animal also supplies leather, wool, gelatin and ingredients used in medicines such as heparin, and that serves a great many people. If we judge by the greatest good for the greatest number, the total benefit to humanity of meat and everything that comes with it outweighs the costs, so ending it would leave people worse off.
The sum leaves out most of what it is meant to add up. Utilitarianism, as Bentham and later Singer framed it, counts the suffering of every being that can suffer. Those are the animals: more than eighty billion land animals slaughtered each year, plus far more fish. A tally that counts only human benefit is not a utilitarian calculation. It is a human-interest calculation using utilitarian language.
The human side is also smaller than it looks. The relevant benefit is not meat against nothing. It is meat against a plant-based diet that already meets nutritional needs. Measured that way, the gain is mostly taste and habit. Against it sit costs that also fall on people: a large share of global emissions, land and water use, antibiotic resistance, and pandemic risk from zoonotic disease. A greater-good argument has to carry those too.
On byproducts, part of the point is fair. Some medicines still rely on animal-derived ingredients. Heparin, for example, is largely made from pig intestine. But byproducts are a small share of a carcass's value. They exist because animals are slaughtered for meat, not the other way round. Most have established substitutes: insulin has been made by microbes for decades, and leather, wool and gelatin all have alternatives. Where no substitute yet exists, that is a case for keeping that specific use and developing a replacement, as the definition of veganism already allows. It does not justify the dinner plate.
Run the calculation in full and it points the other way. That is why so many utilitarians end up vegan.
Presenting only the evidence that supports a conclusion while leaving out evidence that tells against it.
How it applies here: It invokes a greater-good calculation but tallies only the benefits to humans. It leaves out the suffering and deaths of the animals, which the framework requires counting, and the climate and public health costs to humans themselves.
Presenting two options as though they were the only ones available when further options exist. Also called a false dichotomy, or black-and-white thinking.
How it applies here: It compares eating meat with having no food, medicine or clothing from those sources at all. The real alternative is plant foods and existing substitutes for most byproducts.