Humans have been eating meat for many thousands of years.
You say it's wrong to harm animals and use them as food, yet thousands MILLIONS of animals are consumed by other animals every day, so are the carnivores to blame? Is it their fault that they need to eat meat to survive? Are you really that ignorant and handicapped, we eat meat because we NEED to, as Badspot put cleverly, the only substantial source of Vitamin B12, which you cannot live without, comes from eating meat or your own shit?
If you honestly think that animals are suffering needlessly, that is different, if they are tortured to death, that is wrong and I agree with that, but to think that animals suffer needlessly outside of the torture and slaughter, you are wrong. Do you cry when you see a lion tear the shit out of an antelope on the Discovery Channel? Do you really think that slowly killing yourself is cool? Without Vitamin B12, your nervous system suffers, and will fail over time, and you slowly become a vegetable (Funny isn't it?).
Suffice to say, being a Vegan is nothing but a new age Self Delete method, you can and will die without B12 in your diet, I suggest you all study how the food chain works.