You say he was missing the forest for the trees and then completely fall into correlation = causation. The beef patty is not what makes people fat. It's actually one of the healthiest parts of the burger. If people just ate the patty from a big mack and not the sugar saturated buns and sauces, and the fries and sodas, it would not be an issue. Veganism is not going to solve the fundamental issues with fast food. Most of the items that really build up the calorie count with little nourishment are the vegan items that come with a fast food meal. That's not to say vegan items are unhealthy, but that the ones found in a fast food restaurant are.