And what a lot of vegans try to argue is that heterotrophic energy transfer is unnecessary.
Humans consuming plant matter constitutes heterotrophy. Until you sprout leaves and start photosynthesizing (no shade to any plant therians) you will always need heterotrophic energy transfer. Keeping animals as pets, or even just letting animals exist requires heterotrophy. Animals eat plants. Plants eat animals. Animals eat other animals. Obligate carnivores would cease to exist if they were prevented from eating other animals. You've created a moral system here that demands the extinction of any heterotroph, including humans. Personally, I'm not a misanthrope, and I also like seeing birds of prey out in the wild.
