So consider the "what caused God?" question. Recall that Dennett himself affirms that only things which have a temporal origin have causes. It follows that since the Creator of the universe has no temporal origin it has no cause. Now you're right that this conclusion doesn't follow from the premises of the
kalam argument alone, but from Dennett's own additional assumption. What we can say on the basis of the
kalam argument alone is that whereas the universe must have a cause, no reason has been given to think that the Creator must have a cause. Ockham's Razor, which enjoins us not to postulate causes beyond necessity, will therefore shave away any further causes. Given Ockham's Razor, we are justified in positing only such causes as are necessary to explain the effect. Therefore it would be unjustified to postulate a plurality of causes. The ball is then in the opponent's court: he has to give good reasons to think that even timelessly existing entities must have causes—an assumption which is, as Dennett discerns, highly implausible and widely rejected by metaphysicians, whose ontologies often include uncaused, eternal entities like abstract objects.
Reasonable Faith: Question 131 - God as the Cause of the Universe <--- click