If there were a human serial killer killing people via a projectile energy weapon that always instantly killed someone from a long distance before they had any idea what was happening, I don't think you'd argue for a greatly reduced sentence due to their humane method of disposal. If there were an ancient human civilization that went on hunting trips to kill and eat humans in other villages because they believed human flesh was the most prized meat, and they defended it by saying that they were probably all going to soon die of war or starvation or disease anyway, I don't think you'd just go "oh yeah true" without batting an eye.
The sole reason - the necessary and sufficient reason - hunters find hunting justifiable is they attribute no moral value to the lives of non-human animals. Anything else is self-serving rationalization. If you attribute no moral value to them, that puts you in the company of almost everyone who's ever lived, but just state it plainly instead of trying to wiggle around it with mental gymnastics.
> The sole reason - the necessary and sufficient reason - hunters find hunting justifiable is they attribute no moral value to the lives of non-human animals.
Into this:
> The sole reason meat-eaters find eating meat justifiable is they attribute no moral value to the lives of non-human animals.
Animals do not have similar food-providing mechanisms. When you eat an animal, or part of an animal, it'd dead. It doesn't grow back. It wasn't designed to.
All nutrition comes from plants (or the microbiology around them). All protein comes from plants. Anyone who equates the barbary of eating animals with eating plants is choosing to deceive themselves and others.
If we admit the idea that some lives can have negative value for example if they consist solely of suffering it would be OK to breed kid burgers so long as they had a pleasant existence up until slaughter at 7 followed by a quick trip to McKid.
I suspect that my moral philosophy and likely yours is simply insufficient to deal with hypothetical persons and we ought to simply reason about how to treat actual beings that exist.