I think, in at least a narrow sense, I have to side with Dawkins' complaint against Expelled. Dawkins was answering the question "What if we just can't find an adequate terrestrial Darwinian explanation to the origin of life?" His answer would have to be something like Francis Crick's panspermia thesis. If you accept Dawkins' 747 argument, then this is the conclusion you have to draw. That is, if you have an argument that shows that theistic explanations for complexity are always and necessarily going to be inadequate, then if there is an explanatory gap concerning how life emerged, then any possible account of it that, using Dennett's terminology, employ skyhooks is to preferred to one that sticks to cranes, whatever difficulties the crane hypothesis might face.
Dawkins appears to merely assert that the ultimate explanation for extraterrestrial life would have to be evolutionary, and that makes him sound dogmatic. But he has an argument for it. It is quite true that William Lane Craig says that it deserves the title of being the worse atheistic argument in the history of Western thought, but nevertheless the appearance of mere assertion generates a misunderstanding.
Erik Wielenberg has argued that the 747 argument is a recycling of an argument found in Hume's Dialogues, and argument that I have called The Inadequacy Objection. I am linking to Wielenberg's analysis as it appeared on Vallicella's blog. I replied to the objection as follows in my essay in In Defense of Natural Theology:
The Inadequacy Objection gratuitously assumes that matter is what is clearly understandable, and that “mind” is something mysterious, the very existence of which has to be explained in terms of un-mysterious matter. But is this an accurate picture? According to Galen Strawson,
This is the assumption that we have a pretty good understanding of the nature of matter—of matter and space—of the physical in general. It is only relative to this assumption that the existence of consciousness in a material world seems mystifying. For what exactly is puzzling about consciousness, once we put the assumption aside? Suppose you have and experience of redness, or pain, and consider it to be just as such. There doesn’t seem to be any room for anything that could be called failure to understand what it is.
On the other hand, matter is described by modern physics in the most mystifying terms imaginable. The philosopher of science Bas van Fraassen writes, “Do concepts of the soul…baffle you? They pale beside the unimaginable otherness of closed space-times, event horizons, EPR correlations, and bootstrap models.”