I think in this case it's more to do with proportionally lower caloric input requirements for a given output mass of meat, although I admit I'm unclear on the d

I think in this case it's more to do with proportionally lower caloric input requirements for a given output mass of meat, although I admit I'm unclear on the details. I wouldn't look too closely for a consistent ethical basis in vegetarianism and veganism, both of which require drawing an arbitrarily defined line between living things it's okay to kill and eat and living things that it isn't, and then treating that as axiomatic. I respect the motivation, but not the result - we all draw our own lines, but it takes an unreasonable amount of brass in a person to try to argue their line should be good enough for everyone.