Because that's how science works? Cats are obligate carnivores. They require a diet of meat. If you are insisting that a diet without meat can satisfy the needs of an obligate carnivores then it is up to you to prove that it is with a large, well designed study that is published, peer reviewed, and repeatable.

That is what the admin was saying. You can't use the claims in a book written by a vegan activist who was confirming his own bias at proof. That isn't proof. It isn't up to science to prove you wrong. Itis up to you to prove you right.