You're a Truck

So the story goes that a little boy arrives home crying because the other kids are calling him names at school.  His dad turns to him and says, "Son, you're a truck."  The boy ceases his sobbing to look up at his father in confusion and silence.  So, his father says it again, "You are a truck."  This shakes the son out of his bewilderment to say, "What are you talking about Dad, I am not a truck, that's just silly."  To which the father replies, "You know me calling you a truck is silly because you know it is not true.  And in that same way, you can know that what the kids at school are saying is silly, because you know it is not true (who you really are)."