It's easy to throw out numbers like 8% until you realize that it represents over 100 million people. Per capita that may be a small number, but in the general scheme of things it means a lot of disgruntled people. I never really thought about it until I went over there and had the chance to interact with various groups, and it changed a lot of my perspective on how China functions on the inside.
I grew up in Xinjiang, arguably the most ethnically divided region in China, so I know where you're coming from. China's approach to taming ethnic minorities is straight forward: various forms of oppression. Besides racism, the other major reason is that minorities in China, unlike those in the US for example, do not want to be Chinese. There's no civil activism because neither side want true equality (both want to be separate).
Back to the original point: the Han peasant class is far greater than any other demographic. That demographic has been responsible for the dynastic cycles for thousands of years. It's still the case today, and the Chinese government is well aware of that. At the same time, the government has to keep stoking the economic fire, promote innovation, etc.
