Social Darwinism is a rather strange idea that tries to apply the theory of natural selection to social, political and economic life.
According to Kipling, the white man has the divine right and obligation to bring "civilization" to other cultures europeans consider to be uncivilized.
We can clearly see ethnocentrism on the way Kipling portrays the non-white populations of the world: watch sloth and folly bring all your hope to naught (...) The silent, sullen peoples/Shall weigh your Gods and you.
No, of course the "Half-devil and half-child" peoples weren't uncivilized, they were just very different from the Victorian-era English society.