This issue should always be looked at from a case by case basis and never in the realm of absolutes. Animals attack for a myriad of reasons, and anyone saying that animals only ever attack because humans make stupid mistakes are...mistaken. The bleeding hearts who spout that crap likely don't interact with animals very often outside of controlled environments. Animals can embody most if not all of the anti-social constitutions recorded in humans including psychopathy, sadism and masochism. There have been,
many,
many recorded instances of unprovoked attacks and 'thrill killings' from a diverse range of animals including dolphins, deer and foxes.
When you dismiss all animal attacks as: "it's because the person didn't get the message." you are at best dangerously naive and at worst a hackneyed environmentalist wannabe.
if a wild cat doesn't like you, you won't be able to let everybody else know what they did to let you know they didn't like you.
that's why people doesn't know what the message for "I don't like you" is, when dealing with a wild cat.
Unless you are yourself a wildcat looking for a good time then I don't like you, **** off and they'll never find your body all sound something like this:
You do not want to run out of firewood after hearing that on a dark night outdoors. Trust me, waking up at 2 am and seeing glowing eyes 50 yards off reflecting the embers of a nearly spent campfire as the screaming continues is absolutely terrifying.
Now that I've slandered all the other animals collectively, time to go after my fellow humans. A large portion of animal attacks (especially domestic) on humanity are absolutely due to human stupidity. 60% of dog attacks, for instance, are on trespassers, not transient dogs chasing people. Now do we consider that justified when it's just a 12 year old who thinks it's fun to yank the dog's chain and then it snaps? Or if the homeowner keeps a beware of dog sign but doesn't leash the dog and a kid on a four wheeler comes tearing through the yard and gets yanked off and mauled (this happened to a neighbor of mine, the kid survived but the dog was put down) is it right? When an environmental activist camps illegally on a known grizzly feeding ground during an unusually scarce pre-hibernation and in his arrogance (due in part to 12 years of experience) with the animals has him thinking he knows better than everyone else and him and his girlfriend get eaten is it the bear to blame? Personally I'd say no.
In the end I agree with
@Wavelength emotionally, but rationally I can accept that sometimes killing is justified on both sides of this spectrum, and other times it isn't. You can live peaceably with animals but you have to respect them and respect where you as a human fit into their environment, be willing to earn your place in that environment if challenged. Even then it isn't always going to be enough. The guy who got killed by the grizzly I was alluding to (Timothy Treadwell for anyone who doesn't know/wants to know) he was intimately familiar with the species that killed him. He advocated for them for years before his death. He died in part because regardless of his love for these magnificent animals he didn't respect their power and their capacity for violence. He allowed familiarity and emotionalism to blind him to the danger, eschewing even the most basic, nonlethal defenses because of how horrible he felt for the bear when he had to use them to defend himself previously. He became complacent with a group of bears he had been around for years and ignored the well known migratory patterns that saw him introduced to different ones the week of his death when he pitched his tent right in the middle of their pre-hibernation feeding grounds. In hindsight this sounds so obvious, but it would be disingenuous to paint it as such. Hindsight is 20/20, the here and now is all to often like running blind even for the experienced.
I hate the idea of killing in the general sense, whether human or animal, but not to the point where I'd give up my life to an aggressor just because "they shouldn't act like that". I spend more time in the woods than most people, I'm occasionally a government contracted tracker for conservation efforts. I've tracked wolves and bears and foxes, had close calls with mountain lions, and been violently accosted by a raccoon, a doe and almost killed by a gar. You can devote all of your adult life to living among, respecting and loving wildlife and still see it snuffed out in an instant of carelessness or just plain bad luck. Walk softly and carry a big stick wasn't always just political commentary on US foreign policy, the term actually started as a traveler's quip in a dangerous wilderness and fits that scenario much better. In the end this question is just a microcosm of the larger question "Is killing ever justified?" and that's an answer everyone has to decide for themselves...and live with the consequences come what may.