If an advanced alien race landed on planet earth and decided to enslave and rear humans for food, for the same reasons we enslave and rear animals for food, would it be morally justifiable?
Given that human beings possess moral agency and higher thought, it should be incumbent on us to allow these creatures to live their lives in freedom.
Freedom is the key. Whilst animals do kill each other in the wild, they are still free from any higher authority. Lions and tigers do not enslave their prey, and they eat only as a means of survival.
To believe we have NOT been visited by Higher Beings is almost as ridiculous as humans eating Animals. Higher Beings do NOT eat us because there in NO nutritional value to eating us. Just like animals, there is NO nutritional value to eating any type of animal. One can get way More Nutrition from Plants and CLEAN Water.