Most really exceptionally stupid people use Windows...
That's what Andrew C. Oliver says in his modest proposal, where he suggests banning Microsoft Windows users from the net.
Even though a bit on the edge (just a bit) I find it an interesting read. Like, if a given make of cars was the cause of horrible accidents every day due to bad engineering, would we still allow such cars on our roads?
Don't get me wrong: I know many bright people who use Windows, and use it well. It's just too easy to shoot yourself in the foot with it, and collateral damages are not always trivial.