National purity is a cause necessitated by political nationalism in the modern era. The idea of having a single ethnic identity, bound by ancestry, is a great unifier and propels people to act in their nation's collective interests, which they otherwise would not out of concern for their own family and group's self-interests. This is why Japan, and then Korea, have adopted ideologies of national purity for their people, who under these ideologies become willing to sacrifice themselves for the greatness of the nation. Does China need to do the same? I don't know. But I do think Han nationalism is driven by the same needs.
China had done the same during the Han dynasty when the Xiongnu fought their campaigns against China and the usual Chinese actors which would have found themselves competing with one another drew themselves into a coalition against the incoming invaders. After the threat was no more the country then began to divide itself. You can have great big nationalism like during the Han dynasty or smaller nationalism like during the three kingdoms period. Yet even smaller nationalism during the warring states period. China would not have been so culturally sensitive to these kinds of issues had it not been for the period of "humiliation" experienced at the hand of western powers and Japan, or the west primarily speaking. The thing is the larger scale nationalism of the modern period is no longer so much an issue about the boundaries of ethnic purity as it is about remaining nationally secure through the state control of various economies of scale. Many ignorant people confuse the two and believe that just because China is as big as it is, the nationalism automatically assumes everyone within its limits to be ethnically same or is forced to become the same etc.
Edited by mohistManiac, 15 June 2012 - 12:04 AM.