The vegan agenda shows when they crumple everything animal under "meat" and everything vegetable under "vegan", when there are some vegan foods that have higher cost to the environment to be produced than some animal products, when comparing nutrition to nutrition values.
Even if you don't group meat and vegetables in naive ways you still reach the same conclusion:
"Regardless of whether you compare the footprint of foods in terms of their weight (e.g. one kilogram of cheese versus one kilogram of peas); protein content ; or calories, the overall conclusion is the same: plant-based foods tend to have a lower carbon footprint than meat and dairy. In many cases a much smaller footprint."