I eat eggs and lots of veggies, and survive winters pretty well. Again, you are taking it to the extreme... the OP says, that 2oz/meat daily is fine, the body can handle it. I am NOT speaking of being fully vegan but a compromise. But I agree with veganism too. Spiritual people have preached throughout the ages in favor of veganism/vegetarianism. Nothing new.
today meat is improper to consumption anyway... how did norwegians survive then? Because they were making sure to grow lots of crops during summer time and canning/drying as much as possible for the winter. No secret.
what may for a long period of time does not work eternally, centuries ago for example, people were dying from other diseases and killed by wars... so there is no real data about it but the life expectancy chart is a good hint although not accurate too (people were dying young meat or not) , as it says that people live longer today but thanks to bigpharma keeping people on life support
what you say is pointless.
today we do have the technology and the knowledge to grow plants everywhere on the planet... but further so much grain to feed the world livestock is clearly unsustainable.
In china, you have this annual dog hunt and they make them suffer until the dogs die, claiming that it makes their meat tastier. The animal suffering is caused by meat overproduction/overconsumption mainly. Massive slaughter may have the same effect psychically.