Check out Karl Popper’s arguments. I’d link you, but I’m having a hell of a time finding them (which sucks because he was one of my view’s larger influences).
For my points, it’s simply that through any analysis, farming animals is more net utility than not. I actually hold to it by positive Utilitarianism as well as Negative.
First is the utility of people consuming them (if there wasn’t any, everyone would just drop meat-eating in a heartbeat). There is undeniably utility in consuming meat/dairy. In a vacuum, this isn’t everything. Obviously there’s utility in a starving person committing cannibalism. In a counter-vacuum, it’s still not-nothing, since there is arguably negative utility in a plant being eaten (just not much).
Second is the utility in domesticated animals. The alternatives are wild animals or anti-natalism. For the former, there is no question that even the worst case “veal cow with botched slaughter” is better than the best case of wild animals (life of constant starvation and fear, ended slowly and incredibly painfully). As for anti-natalism… I hold with Karl Popper. To exist and feel pain is better than not to exist. Farm animls have plenty of positive-utility moments.
Third is the Utility Monster scenario. HUMANS are Utility Monsters, as compared to animals. This is not to be confused with human exceptionalism. Cows are not planning what to name their grandchildren, waiting for Christmas Dinner. They’re not excited for a delicious meal, slow roasted for 12 hours. The truth is, there is more Utility to 1000 families eating a hamburger or a steak filet than a slaughtered cow living 1 more year, even 10 more years. If one argues we are of equal utility to animals, then I do not see justification that any being should have less utility than any other. And that includes insects and, yes, plants. Either qualities of a species affect utility or they do not. One cannot have their cake and eat it.
So to sum it up… There is no disagreement that agriculture creates net positive utility for humans, right? Well, I have shown that agriculture also creates net positive utility to animals. Disagree or not, even if you could somehow poke holes in some of those points, there is an avalanche of Reason to the idea that a non-vegan world is simply better than a vegan world.