Most people teach their children to be aware of strangers. Why? The facts (but why bother with a simpe thing like 'facts' when you can watch Fox News, right?) point out that when a child gets molested it's usually done by a family member, a teacher or someone else they trust.
We are twenty times more likely to be killed by a relative than by a terrorist so why are we afraid of terrorists and not of our grandma? And in most cases when people are killed it's by their own hand.
So if there's anything or anyone we really should be afraid of it's ourselves.