We are aiding the keeping of the natural balance very well? Huh? We've totally f***ed the natural balance of the earth. The only way you can excuse the scars humans have put on the earth is to completely ignore our supposed free will and just consider us animals. I believe that since we have the ability to understand the whole system we should be more careful not to totally ruin it.
Humans generally do not eat animals they consider to be intelligent. Most people, even the most rabid meat eaters, would never eat a dolphin or whale, nor any other primate, nor cats or dogs. There are cultural exceptions, of course.
I knew a man who was a vegan, in training to become a veterinarian. He was hired to do some handyman work and was asked to trim some brush at the back of the property. He quit. He explained that the plants didn't ask to be cut and weren't hurting anything, and so therefore he couldn't do it in good conscience.
I still wonder what that guy eats now. There's nothing left.