The Koran is obsessed with non-Muslims. They (the non-Muslims) are portrayed as willingly disobedient to Allah, not to be trusted and dangerous to the true believer. This also triggers an innate fear-response, especially in children. Belonging to a group, being accepted is a basic need; hence in-group out-group differentiation is in the innate behavioral repertoire of humans. There seems to be a neurological basis for this; "A few fear responses in humans seem to be innate. Around the eight' month of development, for example, a child usually becomes capable of distinguishing the familiar face of his mother. At this time the infant reacts with anxiety to the face of a stranger (eight-month anxiety, stranger anxiety)." - Kaplan & Sadock: Modern synopsis of psychiatry DSM III -.

If you are a parent, you probably recall this from your own experience. The child suddenly becomes fearful without having had negative experiences with strangers. The cause is the normal healthy development of its nervous system.