Self-defense is one thing, if it's between you or the animal. As is initiated aggression without a way to avoid the attack or being able to talk it down. But even then it should only be to protect yourself, not to harm the animal, imo.
The same is true for humans. You have no idea what they went through to become the way they did. Until you make it a point to find out, you have no grounds for judging it. Or its actions. Nor do you have to find out, but then navigate its territory with care, not with hostility.