This excerpt is taken from this source.
I have just defined a sanctuary as a place where man is passive and the rest of Nature active. But this general definition is too absolute for any special case. The mere fact that man has to protect a sanctuary does away with his purely passive attitude. Then, he can be beneficially active by destroying pests and parasites, like bot-flies or mosquitoes, and by finding antidotes for diseases like the epidemic which periodically kills off the rabbits and thus starves many of the carnivora to death. But, except in cases where experiment has proved his intervention to be beneficial, the less he upsets the balance of Nature the better, even when he tries to be an earthly Providence.
I did not comprehend the meaning fully. For example, what the author wants to say does away with his passive attitude in this line
The mere fact that man has to protect a sanctuary does away with his purely passive attitude.
I have also confusion to understand the whole meaning of this reading comprehension. Could anyone help me to understand the main theme.