What examples in Kim portray Kipling's view on human nature?
You might want to consider the character of Teshoo Lama and what he brings to the novel. It is through this character that Kipling strongly suggests the theme of unity and equality in man. This is of course a very important theme given the Indian caste system that Kim is so familiar with, as the Lama's teachings point towards the limits of such heirarchical structures and insist on a unity and brotherhood that all humans share. Note how he instills this sense in Kim through his teaching:
To those who follow the Way there is neither black nor white, Hind nor Bhotiyal. We be all souls seeking to escape.
In the Lama's view of the world, what is most important to understand about human nature is that we are all united and all the same, rather than focusing on the ways that we are different and how we divide ourselves from our fellow humans. The repeated references to the Buddhist Wheel of Life and the Lama's eventual attainment of Enlightenment serve to verify this as an important theme of the novel and indeed it suggests that equality and unity are important and vital aspects of human nature.