I would agree that it's a bit excessive. Do they eat little fuzzy ducklings in the wild I doubt it. They do jump though so I'm sure in the wild they might get a few baby monkeys so really what's the difference. So no not cruel to me, a bit excessive yes.
It's been discussed many times and always ends badly. Based on history, there isn't any need to discuss the issue. Since fish do not need to eat mammals or birds in an aquarium as part of their diet, I would hate to see anyone receive sanctions because of an issue that results in emotional posts from some members. There is plenty of information on the subject.