Vegans and vegetarians can move along and enjoy their day. You're cool already, and off the hook.
Cows are ruminants. That's a group of animals that are specially adapted to eat nutritionally-useless grasses. That's their whole deal. If you're living in a pastoral or premodern farming society then that's great because you can't eat grass and you can eat cows, so it's free food. But instead you live in a society (insert meme) where we grow food specifically for cows then ship it to cows. Again, the animal that's specialized in eating things that have no nutritional value, so we're going out of our way to grow plants with no nutritional value, and then ship enough of it around to feed an animal anyway.
What does that mean? It means by whatever metric you choose, cow meat is worse than half as efficient as other common sources of animal protein.
Feed conversion ratios. Enough feed to make a pound of beef is enough to make 2.5 pounds of pork or 5 pounds of chicken.
CO2 per calorie. 1000 calories of beef costs 13.8 kg of CO2. 1000 calories of pork costs 4.45kg CO2. 1000 calories of chicken costs 3.37kg CO2. Also note lamb topping the charts, which will be a running theme. (Also an extra reason not to use broccoli as your primary calorie source, if eating 13 pounds of broccoli a day wasn't a good enough reason on its own.)
Land use per year per calorie. How much land did that 1000 calories take? You'll need 119 square meters for beef, 7.26 square meters for pork, or 6.61 square meters for chicken. Note lamb topping the chart again. (Also apparently prawns can be farmed super dense, that's something interesting that I didn't know.)
Why do sheep show up so high on some of these charts? Because they're also ruminants. Don't eat sheep either.
I've always wondered how people can recognize the moral implications of eating meat and go vegetarian, but excuse/ignore all the harm the dairy industry inflicts to animals. Vegetarianism should be morally opposed in almost an equal way to how vegans oppose eating meat, unless it's because you're trying to transition to veganism. I really can't get past how certain vegetarian cannot see the hypocrisy of opposing the meat industry and yet continuing to fuel the dairy one
Mega necro posting but as the post was just linked in another thread fuck it I thought I'd answer. As a vegetarian and with many vegan/vegi friends I'd say the answer is mostly effort, most vegetarians do understand its not great, but its in the similar way that buying clothes made from sweatshop labour isn't great or the use of cars that emit pollution isn't great.
We all do things that suck because society has made these choices the easy option. We can go against them but it requires effort and it will be a whole lot of effort if you want to make each of your life choices the most ethical. I'm like 99% vegan as I don't drink milk or eat eggs straight, however I don't really care that much if its a small ingredient in something pre-made.
Its about how much effort you are personally willing to go to relieve suffering in the world, personally it stops for me at being flexible on veganism