So long as he limits himself to rejecting abiogenesis, and not the patently obvious science of evolution, then whatever.
My attitude remains this: the burden of evidence is on those who claim that deities exist. I haven't any problem with the idea that there is something beyond the observable universe, but rather the idea that we have even remotely enough information (we have none whatsoever) to validly speculate what that might be.
That the universe is here is obvious. That it is complex is also obvious. To proclaim failure in the quest of understanding that complexity achieves nothing but to displace the exegetic mystery.
In other words, to follow this line of reasoning, if God 'must have' created the universe, then what created God? So, Flew falls prey to the god-of-the-gaps. He says: "I don't have the answer, so I'll just make one up!" Oh well.
PS. I also think most people are better off believing than not, so long as they don't interfere with scientific progress beyond the limitations they impose on their own rationality.
If all matter is made up of matter, what was there before the first matter?
We have the same problems with time as we do with matter. Yet matter exists, we can know it though our senses. Some things we can know exist that we cannot know using our senses alone. There are many such things for you. God is one of them, but it has not quantity, size or specific location. So seeking this knowledge with science alone is like trying to see the periphery with a telescope. It's the wrong method for the empirical knowledge sought.
there is something beyond the observable universe
Transcendent. Many things you know transcend your sense detectors. It is the unobservant one who clings to the illusion that all he knows about reality he knows by sense and reason.
Flew falls prey to the god-of-the-gaps.
I recognize the old reference, but my point is science has gaps as well. By design it limits what it can know. It limits it to those things detectable by the senses (and their extensions) that have simple location, size and quantity. That all of reality conforms to these restraints is a leap of philosophy, not science. And it's a leap made two centuries ago that fell upon it's own weight within a decade. Yet it lives on in the popular mind - and in the mind of some scientists who don't realize they are very poor philosophers and theologians.
The fault some make is to slide lazily to the false conclusion that if Science cannot know it, therefore it doesn't exist. Neither Science, nor reason, can prove this. It fails on it's on logic.
so long as they don't interfere with scientific progress beyond the limitations they impose on their own rationality.
Why interfere with your own progress by imposing the limits of rationality upon it? If you look closely, you will see you know a great deal more of reality that can known using science or reason alone.
You have all the equipment you need; observe yourself.