I agree, that was a strong follow up from Dr Zee.
The thing is, Bob makes the case for God's existence by insisting that the naturalist's position is impossible. Zakath insists that it is not, and illustrates it by outlining some hypotheses that represent our first steps into the deepest mysteries (where did life come from, where did the universe come from).
There are a number of advantages to the naturalist position:
Hypotheses are, or may one day be, testable. They can be discussed, debated, modified and discarded. Even discarding is useful, because it tells us something that couldn't have happened.
Fiat creation is not testable. There will be no hypothesis of creation beyond that of the admittedly pleasing verse of the OT. Many (most?)
Past experience has shown us that lines in the sand about what is knowable have always been crossed. As we only have history as a guide, I select science over supernaturalism. We've only really been doing this for 400 years, why not give the process some real time?
However, sometimes it seems that no amount of evidence will satisfy a creationist. If one day scientists demonstrate abiogenesis in a lab, the creationist will say that it proves intelligent design, and anyway, there's no evidence to say that it happened that way. Most creationists may not be really interested in truth, but then again they'd say the same about me.
Furthermore, while Bob pussyfoots around and won't declare an interest in one deity or another, then all manifold possibilities open up. It seems he might have to use the same science he criticises to negate the creation myths of others (geology, cosmology, physics) - if he does not then surely he is forced to place Christianity on the same footing as all these other religions. This is a position I doubt he is willing to take.
Again, the naturalist has the advantage here. And atheistic naturalism is the default position - be skeptical about all such claims. Rely on what we know and what we believe we know. There is no "proof" for theism to be found here.
Actually, there are a couple of better arguments Bob could marshal if he insists in staying within the physical realm, but I'm not going to be helping him out.
Novice, the point is that if there are alternate possible explanations for some of these fundamental questions (and there are, although they are extremely tentative), then the existence of the universe and life ceases to be proof of God's existence. Furthermore, if a naturalist explanation is found, it then negates a key reason for the existence of a hypothetical deity or deities.
Finally, remember that Zakath is also being asked to prove a negative -- always a toughy. There are many things I don't accept that I can't prove away beyond a shadow of a doubt. I don't really believe that aliens are visiting this earth. I don't believe that fairies really exist. I don't believe in angels, guardian or otherwise. I don't believe in a secret conspiracy that runs the planet.
Lots of people do believe some of these things, and to prove otherwise to their satisfaction is next to impossible. "If only you would open your eyes and drop your preconceptions", they say, "then you would see the truth."
If Zakath can cast reasonable doubt on Bob's arguments, then Bob has failed to prove the existence of God. It will then be up to Zakath to summarize why the evidence (or lack of it) favors his position. There are still quite a lot of posts to go, Novice.