So that is the problem the Chinese government needs to solve. Keep order and harmony, because for the vast majority of people, it's better than chaos. (Look at what happened in Egypt recently when they had their new government.....lots of violence, then nothing really changed. Replacing Mubarak was probably a mistake, but some people paid for it with their lives).
With a different form of government, unscrupulous men can start a campaign of lies, and build a following, and if he's convincing enough, even make it into power as president. But all this will happen without real violence (that is, violence does not lead to power and political enemies don't need to 'disappear'), and the system is designed with power balances to prevent things from getting too messed up, even with a lousy president.