Humans certainly do kill cats both for food and "fun". And orcas will, from time to time, kill things that they don't eat. Even the exclusively fish eating orca

Humans certainly do kill cats both for food and "fun". And orcas will, from time to time, kill things that they don't eat. Even the exclusively fish eating orcas in the Pacific Northwest have been witnessed killing seals, even though they never eat seals. Not being afraid of orcas is a show of lack of respect for them. They can weight up to 10,000 pounds, swim at bursts of 35 mph, swim at slower speeds for huge stretches, launch their bodies tens of feet out of the water, and kill anything from salmon and rays to great white sharks, humpback whales, and even blue whales. There is a lot of argument that they may be the greatest predator ever, on land or sea. A domestic cat can easily wound a human and can usually get away. That is not true of a human in the water and an orca. Yes, orcas are extremely, extremely intelligent, and there's zero reason for them to eat us for nutrition, as they are highly tuned eaters that maximize their calorie intake per effort. However, a human is completely within an orca's decision process as to whether the human lives or not.