I'm not sure I quite understand exactly what you're trying to say. I think what you're saying is that there's a big difference between killing your own pet/livestock for food or killing a predator, even if its some one elses pet, for harassing livestock and someone kidnapping a persons pet with the intention of slaughtering it for food (or some sort of amusement).' The latter is a depraved action stemming more from a blood lust not a need for food or desire to learn.

My family has raised and slaughtered (or had slaughtered) livestock since I was six. And I have no problem with my uncle killing pet dogs that pack up and attack and kill livestock. And I've held several pets, my own and other peoples, while they were put down when I worked at a vet clinic. Killing an animal is often called for. But killing for amusement or bloodlust is repugnant to me. I'd be inclined to treat the person who kidnapping the tortoise more like the cat in your post since that's what their behavior is in my mind.