Steven Landsburg asks a very good question:

" So what's the moral of the story? To me, the moral is that we should take seriously what we tell our students (...citizens, colonial subjects, whatever - ed.) ... If it seems not to be working, the right question is not, 'Why doesn't [what we tell our students, citizens, subjects...] work?' Instead, the right question is [...] 'In what way am I being stupid?' "

This oldie but goodie via Defective Yeti.