"Prove ...that the Creator never gave permission to eat them"
The same logic that prohibits us to take the life of humans.
Why do you think that animals are of less worth than humans?
You would found it reprehensible with someone killing their dog, cat or your horses. I agree it would be terrible!!
The Creator's other beings are of NO less worth.
Assuming a holy book to be true, so many people have hardened their hearts; and think it is of okay to kill some of our Creator's sentient beings.
The Creator gave their lifespan. Who are we to shorten it??
He gave our lifespan and their lifespan for a reason. Slaughter houses many time reduce their life span more than 10 times.
I write only this because I care of you and care of the animals:
You may assume it to be right to take the life of other beings; but it will never change reality.
Reality is that there are no proofs at all that the Creator allowed men to take the life of animals; and that we should take care of His creations -- not kill them!!!