Harambe
It is clear that you are unlikely to be interested in the legitimacy of me killing a mosquito on my own territory, for example. Moreover, you would hardly notice if I killed a mosquito on someone else’s territory, unless I was explicitly told that it is a valuable mosquito in private ownership and must not be killed.
It is also not certain that you would be very interested in the legitimacy of killing various meat animals in slaughterhouses for the purpose of subsequent meat sale, although there are people who do contest it. Unfortunately for them: all this meat livestock lives only as long as its breeding is profitable. No profit—no livestock. The population of cows, pigs, and other rabbits will decrease sharply, and those excess to the capacity of the natural habitat will either starve to death, or people will have to carefully eat them without reproducing the existing herds. As soon as humanity manages to set up the production of synthetic meat that is cheaper and tastier than the natural kind, this exact scenario will happen: no one is interested in cleaning up manure when a steak is printed on a printer.
But, judging by your nickname, you are not talking about animals in general, but about rare ones, whose natural habitat is negligible, and who live almost exclusively in zoos, primarily so that people pay money for the right to look at them. These animals are luxury items, and, of course, no one will kill them without serious grounds. The accident with your namesake was a situation where everyone involved suffered: the child who was injured, the mother who experienced serious stress, the zoo, which, to avoid the costs associated with the possible death of the child, was forced to destroy a valuable animal, and finally, Harambe himself.
We do not know how soon zoos will stop being profitable because people will find it repulsive to look at animals in cages. When that happens, nature reserves will be the only places left for animals to live, and people themselves will visit them in cages, or some other way that does not violate the animals’ privacy. In general, the more resources a human is able to obtain without serious transformations of nature, the less their need for those very transformations. In a world where all of a human’s material needs are satisfied by a thought, practically the entire planet will be in the power of virgin nature. That is the kind of harmless animal we are.
