Excerpted from said article:
"Even if one accepts the 90 percent Han number, which is a problematic one (there is always something vexing about trying to define the exact boundaries of such categories), there are many groups of people within this capacious majority catchall group who speak mutually unintelligible dialects and have radically dissimilar customs. To cite just one illustration, the Hakka, or "guest people," scattered around China are considered Han but have many characteristics that, in another context, might easily lead observers to categorize them as "ethnically" distinct from those they live among. There are many historical cases of what would seem typical outbursts of communal violence or "interethnic" conflicts that pit Hakka (who, among many other things that have set them apart from their neighbors, never embraced any form of foot binding, a practice that was far less uniform than outsiders have often suggested) against non-Hakka living nearby.
Further complicating the issue is that people from various Chinese regions often view one another through a lens of difference. Residents of Beijing view their counterparts in Shanghai as utterly unlike and inferior to them — and Shanghai residents return the favor. The dismissive and dehumanizing terminology that some Han urbanites use for Han migrants from the countryside, in which the former imply or state that the latter are less than fully human or just like animals, resembles what Americans describe as racist when skin color is involved. Location and point of origin are thus a crucial source of diversity in China today, as is when, rather than where, one was born."
--Foreign Policy
The Myth of One China (Jeffrey Wasserstrom)
Apr. 13, 2010