Theologians attempt two (mutually incompatible and pathetically inadequate) answers to this unanswerable point. Some say their God is not complex but simple. This obviously won't wash. No simple god could design bacterial flagellar motors or universes, let alone forgive sins or impregnate virgins. Presumably recognizing the justice of that, other theologians go to the opposite extreme. They admit that their god is complex but assert that he had no beginning: He was always there and always complex. But if you are going to resort to that facile cop-out, you might as well say flagellar motors were always there. You cannot have it both ways. Visitations from distant star systems are improbable enough to attract ridicule, not least from the advocates of intelligent design themselves. A creator god who had always existed would be far more improbable still.
The sort of complexity theologians argue against when they call God simple is philosophical complexity. God is not difficult to explain: He isn't merely powerful—He's all-powerful. He isn't merely intelligent—He's all-knowing. God, if He exists at all, must be simple to the extreme. One argument for God's existence, suggests that if He is possible, He must exist in all logically possible universes. This might be difficult to understand, but it's simple to describe. Bertrand Russel noted of that argument, "it is easier to feel convinced that it must be fallacious than to find out precisely where the fallacy lies."
Further, as any Darwinian would be fully aware, complexity arises from simplicity all the time. The elegance of Darwin's theory is that a relatively small and simple set of rules could explain a mind-boggling variety of species. One of the joys of reading Richard Dawkins' non-religious books is the detailed descriptions of extraordinary species and conjectures about their origin. To cite another example, the mathematics of fractal geometry shows how simple rules produce the most amazingly complex, almost organic, shapes.
On the other part of his argument, Professor Dawkins seems even more out of touch with the subject he expounds upon. Surely he can't be unaware that philosophers from pre-history until this very day have known that the simplest and most probable explanation of an entity's origin is that it has always existed? Until forced by the evidence discovered nearly 100 years ago, secular philosophers have universally taken the universe to be eternal. God, if He exists, can have no origin with a probability of 1.
This technique of arguing against a theory by setting up its most plausible version and dismissing it is commonly used in science and philosophy. The late, great evolutionist John Maynard Smith used it in his 1964 attack on the then-popular theory of "group selection." He set himself the task of devising the best possible argument for group selection. The details don't matter; he called it the Haystack Model. He then proceeded to show that the assumptions that the Haystack Model needed to make were highly unrealistic.
I must claim ignorance of John Maynard Smith's work, but it sounds an awful lot like a straw man argument (oddly enough). Generally, the technique of building your opponent's position so that you can knock it down is considered a fallacy. Again, I can scarcely believe Professor Dawkins could be unaware of this. Only if one earnestly creates the strongest possible argument would it be valid to claim victory when the argument is refuted. So I struggle to see how the "alien theory" could be considered by anyone to be the best Intelligent Design theory unless God is ruled out a priori.
And that, of course, is the problem Professor Dawkins has. He isn't defending himself against people who believe Intelligent Design (there are much worthier opponents) but against other atheists. It would appear that he was caught making fairly ridiculous claims in the documentary and is now attempting to right his ship with somewhat less ridiculous claims in the opinion section of the LA Times. Unless he can correct his delusion that he is a philosopher, I doubt that he will succeed.