Animals kill for food and to protect their babies....?

humans kill humans for thousand of reasons

Killer Whales and dolphins kill for sport (Orca are actually the largest porpoise in the oceans).

Male lions sometimes get bored and go and kill a cub or two of his own and not eat them.

Your average house cat and some small terrier-type dogs will kill birds, mice, rats, rabbits, etc for sport - they usually will not eat it.

There are many instances of wild elephants attacking villages and killing people for no known reason.

A bovine bull who seems docile will sometimes maul it's caregiver for no reason whatsoever.

There are many other examples in both wild and domestic creatures.

some animals kill for safety, and a few kill for status. Male sea elephants will combat until demise to grow to be the alpha sea elephant. Even rabbits, who're prey animals, each now and then kill one yet another over territory (they are very territorial). there are a number of many obtainable who kill one yet another for different reasons than nutrition.

Dolphins also kill for sport.

humans got kind of merciless when we became top of the food chain