I think the chief obstacle to preventing stupidity without preventing cleverness is that there are clever ideas you haven't thought of yet that sound stupid. There's also the fact that what is stupid under one set of circumstances is clever under others.

Suppose I was designing a new car radiator, and I decided that I wanted to prevent idiots from, say, filling it with motor oil, so I built a system which would prevent the addition of anything other than water or antifreeze. Then suppose the radiator sprang a leak. At this point, the owner of the car might want to use the old shade-tree mechanic's trick of putting an egg in the radiator that will flow to the leak and produce a plug (or, more intelligently, a synthetic compound that does it more effectively and with less likely damage to the machinery) ... but they can't, because of the thing I did to prevent stupidity.