We've taken the dog as an example of how animals are sold, treated or abused. For all kinds of animals goes that they have to (let themselves) adapt to people, in appearance and in behavior. This is done by breeding, with all kinds of drawbacks. Is this justified?
We claim the right to take animals from their natural habitats, for instance birds, snakes, lizards, turtles or exotic fishes. Is this justified?
We put birds, guinea pigs and rabbits in tiny cages, or fish in tiny bowls, so that we can look at them whenever we want. Is this justified?
When we can no longer keep the animal, we sell it, take it to the animal shelter, where some of them are put down, or we free it outside somewhere to fend for itself. Is this justified?
We make sure that dogs and cats cannot reproduce by sterilizing them or removing their testicles. This is also done with rabbits and guinea pigs because otherwise they "smell", and with dogs because they show natural behavior we do not like. Is this justified?
That's why we discourage keeping pets.