There is tons of evidence if you would not refuse to look. Especially social animals (for example pigs and cows) would outcast individuals out of their herd. They are also quite intelligent. But hey it is comfortable to pretend we got some high ground while we all know that animals have feelings and that what we do is cruel beyond imagination. And all that to just satisfy some urge for a special taste and convenience. I wish people would at least not pretend its ok.