It's not an emotional argument, if a vegan diet requires 1/10th of the acreage, then it requires 12 dead mice as opposed to the 120 dead mice + _whatever animals you're eating_ of the meat-eating diet.

A meat eating diet inherently requires more acreage due to thermodynamics. It works like this: 20 acres of grain feeds 10 cows which feeds 1 person for a year, therefore 240 dead mice and 10 dead cows. An omnivore's diet inherently requires more acreage, therefore more dead mice and all the cows, chicken, fish, &c. you're eating.