I'm going to steal my nephew's pet tortoise
Why would you steal his pet tortoise?
I think I can sell it for good money.
Pets are like family members. You should not steal anyone's pet, especially your own nephews. It's just like kidnapping.
I think he can survive without a tortoise, it's only an animal.
It's not just an animal, it's a living thing. Even if it was an inanimate object, you have no right taking people's things.