Thanks for giving this a serious reply. After I wrote my reply, I started worrying that you would think I was just being snarky. Luckily you didn’t.
I agree with most of what you say. I don’t think the “initial cull” is a big problem anyway, since the trend away from meat is going to be gradual.
I don’t entirely agree with your argument about most domestic animals being treated so cruelly that it would be better (for them) if they had never lived. I do cringe at factory farming methods, but, the other hand, having lived much of my life in rural areas, and even though not having ever raised animals for food myself, I have friends and neighbors who raise livestock humanely, even lovingly. I know it seems sort of paradoxically if your aim is to kill them and eat them, but the fact is, I know farmers who treat their cattle and pigs during their lives as lovingly as I treat my horse. What is more, although I recognize that horses by nature prefer to roam widely in large herds, I do not think my comfortably pastured horse lives a life so miserable that he would rather have never been born. Personally, with regard to eating meat, I come down to eating less meat than I used to, and eating meat that is humanely raised, preferably by farmers I know personally, and of course “sustainably” raised at least in the sense of eating grass rather than grain.
I don’t mean to burn up a lot of your time with dialog over humane vs inhumane farming methods, but I would like to have another try at posing one aspect of my question which you did not directly answer. That is this: Let’s posit that all sentient beings have value. Given that, the question is whether preserving a species is ethically important in and of itself, aside from the welfare of the individual members of that species. (I do not mean just instrumentally important from a human point of view, like preserving the clotted milkweed or whatever because we might get a useful medicine from it some day.)
To put it in a “trolley” frame, suppose you send the trolley to the right, and it wipes out the last breeding pair of black rhinoceroses, but guarantees the long-term survival of a large wild population of white rhinoceroses; whereas if you send the trolley to the left, you guarantee survival of both species, but only a minimum viable number of individuals of each, all of whom are to be confined to zoos.
The point sounds kind of silly when you put it this way, but I read so much about the importance of preserving species that I am sure there are people who place an ethical value on a species that is separate from the ethical value of the individuals within that species. What makes such a belief defensible?