obtain exclusive mating rights whereas losers gain either nothing or only partial access. The more aggressive an animal is, the more benefits it is likely to gain, but if an animal is too aggressive it might face unacceptably high costs, such as serious injury, so the animal must weigh up the relative costs and benefits of its action and choose an optimum level of aggression. If the costs are too high, and the benefits are too low; avoiding a fight may be preferable to competing. In other cases it may be worth fighting vigorously for a valuable resource. I think that any race, species, or other group of animals feels morally free to torture, injure, psychologically brutalize, capture, destroy, genocide, and generally toy with the lives of less important species while still feeling morally superior by virtue of the fact that they would never do such horrible things to their own kind. Particularly, animals would never kill anyone of their own kind, and look down on other races, who prove their barbarity through killing each other.
Animals don't necessarily think they're morally superior because they don't kill each other. They just think they're better, and the fact that they don't kill each other is indirect proof of that. If they do start killing each other, don't expect them to suddenly realize they're no better. They've probably got tons more reasons why they're better, all of them as irrational as that one.