My guess is intellectual depth, for it appears that Laura Bush is every bit the idiot that her husband is. That can be the only conclusion drawn from her reading of the Iraqi shoe-throwing incident:
It was an assault. And that’s what it is.
Actually Laura, it was one of the gravest curses that can be cast upon a person in Islam, given in a situation guarenteed to produce not only the insulter’s arrest but likely his subsequent torture as well. If you want to go with “assault” you can, but it just goes to show how little you know about the world outside Crawford and just how damaging such ignorance can be.