they seem to be aggressively ignoring the cost of raising livestock. i cannot accept that they genuinely cant understand it, they must be just ignoring it. very puzzling stuff.

Of course. A score against veganism doesn't automatically justify a meat-heavy diet. Especially if it's based on industrial agriculture. Actually I don't even think the conflict here is meat vs vegan diet, but industrial vs sustainable agriculture.

raising livestock at scale to the environment.

ruminants live on their own in the environment, they are part of the environment.

sustainable world

You can't have sustainable agriculture without animals, fertilizer comes from animals or fossil fuels....