The argument for eating animals is very simple. They process things we can't eat into something we can. Cattle eat grass. By eating beef or dairy products, we eat grass. That's important.

We may now have reached the point where our technology allows us to process inedible stuff into edible stuff without the intervention of herbivores. Or not. I don't know. But I do believe that the test of whether it is ethical to eat herbivores is whether there would be enough food for everyone if we didn't.

And, of course, there would be no herbivores on farms if they couldn't be eaten. What would become of their species? Would we be competing with them for the grass we would want to turn into edibles?