Yes! beat me to it! Much of our meat is grown in areas where farming vegetables is either impractical or the land is unsuitable for anything but raising meat animals. Humans cannot eat grass, brush, or trees. Growing plants in areas like deserts or areas with a growing season that is too short precludes growing crops but meat animals do well in these places.
This is not a right/wrong issue and eating vegan in a healthy way is expensive eve now. Bring up the number of people looking to eat vegan the prices go up faster than production of suitable veggies.
Are you going to suggest we raise our children vegan next? Children do not do well on vegan diets, their caloric needs are higher, babies and toddlers have died when raised on a strict vegan regime.
Humans are not vegetarians, veganism is an option that has only been possible in the last few thousand years, before that we ate meat, lots of it. Humans are healthier eating some meat at least. We evolved to eat meat, we exchanged a digestive system that could effectively digest plants for a more meat based diet so we could support larger brains. Even our closest relatives, chimps, eat meat... unless you are going to say insects don't count and they do hunt, kill, and eat small animals including other primates.
http://theconversation.com/is-a-vegetarian-diet-really-more-environmentally-friendly-than-eating-meat-71596
https://www.independent.co.uk/life-style/food-and-drink/veganism-environment-veganuary-friendly-food-diet-damage-hodmedods-protein-crops-jack-monroe-a8177541.html
https://www.cnn.com/2017/02/06/health/vegetarian-diet-conversation/index.html
https://qz.com/749443/being-vegan-isnt-as-environmentally-friendly-as-you-think/