1. Education level of parents does not completely explain the intelligence levels of their children.
2. Numbers have not always overruled technology and intelligence. Intelligent actors usually feed that "dumb mob" their seemingly idiotic ideas and beliefs, and if you look at the actions the mob takes instead of what they say you find there is generally a rhyme and reason. The oratories of Marc Antony and Brutus in Shakespeare's Julius Caesar are excellent examples of this. Just because the common people ultimately acted on Antony's emotional speech instead of the rational speech made by Brutus doesn't mean their actions were unguided or unintelligently motivated.
3. On your last paragraph, you are completely correct: there have been no mass societal uprisings involving exclusively intelligent, educated people. But relating to my second point, all societal uprisings that I know of have been motivated by intelligent, educated actors. The French Revolution, the Russian Revolution, the American Revolution, Fascism in Europe, the Communist Revolution in China... on and on, there is always an educated class that begins and motivates these mass uprisings, and the intended result of the uprising always benefits that class.
A large base of average/below-average intelligence people may be good for society, as long as the upper classes are pushing a rational, progressive agenda. Those rallying behind the banner may not be the brightest, but those creating the ideas embodied by that banner are usually pretty intelligent.
