I feel like you and Rayiner might be talking past each other. I read him to be saying that the moral argument you'd get from cutting meat wouldn't be worth much, either, because the US would still be emitting multiples more GHG than developing countries, even if they drove overhead from meat farming to zero.

But that’s the thing, if that’s his argument I disagree as well.

Simply put no matter what the reason to oppose meat consumption in the US still holds up. It’s a great improvement in real terms & it provides a stronger moral argument.