The article should be titled something more like 'Local, Seasonal Diets Are Going To Save The Planet'. It's not much about vegetarianism, except to attack it for clickbait reasons.
That's the fundamental blind spot of vegans. Anyone actually growing some vegetables and fruits in his backyard will understand this. I know many starry-eyed hippies growing organic stuff in the countryside, and if many of them are vegetarians (eating dairy, eggs, etc but no meat) absolutely 0% of them are vegans because it doesn't make sense from a producer perspective.
Absolutely, and that's why I said vegetarian rather than vegan. Working animals for eggs, milk, wool, etc are a good idea. That's still not supporting an omnivorous diet though.