The argument against is essentially "Darwinian life is natural". But, many unethical things can be considered natural, but we as a society prohibit them. Rape and murder are natural. You can find them all over the animal kingdom and prehistoric society. Humanity is always striving for a more ethical existence, and as biology has revealed, animals have limited cognition and do not desire pain. Between anti-animal cruelty laws and so on, we always strive for a more ethical world.
Help stop illegal wildlife trade, and reduce conflict between people and animals. For example: more than 1,000 rhinos were illegally killed in three years, the Amur leopard is important ecologically, economically and culturally. Conservation of its habitat benefits other species, including Amur tigers and prey species like deer, poaching, changes in habitat, climate change, human activity and tens of thousands of marine turtles die each year when they become trapped in fishing, shrimping nets and hooks.
Humans should not intervene with death, because when we do that it affects the balance in the ecosystem. Thus if we protect one gazelle from a cheetah attack then that cheetah dies, lowering the population, and the gazelle population grows. This margin might then just be enough to help the gazelle herds protect themselves meaning even more gazelles and even less cheetahs. Then this continues until there is finally no more cheetahs. They then eat all the plants they use for nutrition, and then the whole ecosystem dies off.
The theory of evolution, which was once a novel concept, is now a world-accepted theory that may dictate the rules in the Circle of Life. Though it is known that Planet Earth crew watches wild animals die, human should not intervene in the Circle of Life; for their interruption may unequivocally alter a subsequent evolutionary process, which is necessary to the progression of the Circle of Life. For example, let's say that a lion cub has just been born. The cub's mother takes her largest companion and goes hunting, coming upon a deer. The lion mother attacks the deer, but is subsequently stopped by humans from Planet Earth crew. What the crew doesn't realize is that by stopping the lion mother from completing her kill, thus acquiring the meat, they have inevitably ensured the death of the lion cub, who depends upon that deer meat to grow and survive. If the lion mother had been allowed to complete her kill, and subsequently take back the deer meat to her child, the child would have had food to eat, in order to grow strong and continue the evolutionary process of lions. Instead, due to the intervention by the Planet Earth crew, the lion mother now has no meat to provide for her child. Therefore, her lion child will die and the whole evolutionary process has been unalterably changed forever. Evolution is a theory, but nonetheless, it is a theory that has been widely accepted as fact. Therefore, humans musn't intervene in processes that we can't understand, and never will.
Humans should only intercede in animal events if they have had some affect on the situation to begin with. In other words, if two animals are together BECAUSE humans brought them there, then it is their responsibility to keep things orderly and safe. If the humans are in the animal's environment and are making a point to not directly interact with the animals and just observe, then the course of events would have been the same with or without their presence.
Without death, society cannot evolve. Darwin was correct that the weak have to die in order for the species to become stronger. People who film television shows should let nature live. It would be interrupting what is supposed to happen in nature, just like when people cause climate change by polluting.