Why are highly intelligent people social outcasts?

People are afraid of anyone they think is superior to them, and if someone is obviously smarter than the people they are around, they will probably be shunned in some way. Also, consider this. If you were smarter than everyone you know, wouldn't you want to be away from those you consider inferior? Those great men you listed probably felt like they were baby-sitting two year olds whenever they were around normal people, constantly having to explain every little thing that they consider common knowledge.