There is none so blind as he who will not see

From an article in the LATimes about the "White Cemetery" in Kabul:

For 25 years, the cemetery has been watched over and its greenery tended by Rahimullah, who like many Afghans goes by one name.

During the Taliban years, an angry Mullah Mohammed Omar stormed into the cemetery with his gunmen and demanded to know why a Muslim would guard the graves of Christians. Rahimullah tried to sidestep the Taliban leader's question.

"Because I am illiterate and illiterate people are blind," Rahimullah reportedly told Omar.

They don't have to be stupid unless they want to be.