I was listening to a podcast with Raw Egg Nationalist: https://search.brave.com/search?q=raw+egg+nationalist&source=desktop

And he makes the point that yes, even going back 2,500 year ago it was understood that meat makes for boldness and vigor, and that a more controllable society is vegetarian. Socrates says so in Plato's Republic. Again, this is the reason primarily why, not global warming, they want us to turn away from meat.

For the lower classes:

"Here follows a rustic picture of their way of life. They spend their days in houses which they have built for themselves; they make their own clothes and produce their own corn and wine. Their principal food is meal and flour, and they drink in moderation. They live on the best of terms with each other, and take care not to have too many children."

For the guardians:

"But our warrior athletes must be wide-awake dogs, and must also be inured to all changes of food and climate. Hence they will require a simpler kind of gymnastic, akin to their simple music; and for their diet a rule may be found in Homer, who feeds his heroes on roast meat only, and gives them no fish although they are living at the sea-side, nor boiled meats which involve an apparatus of pots and pans; and, if I am not mistaken, he nowhere mentions sweet sauces."

https://www.gutenberg.org/cache/epub/1497/pg1497-images.html