This letter is inspired by several recent (within the past few months) topics on your program. These are the topics of the Moon Landing Hoax video, God and the Astronomers, and Evolution.
This is a rather long message, and I apologize for its length. Basically, the points raised are as follows: http://ritestuff.blogspot.com/2005/05/how-do-we-know.html
Although the weight of evidence shows that the moon landings took place, most people choose to believe or disbelieve it because of their preconceptions about the credibility of sources.
The call to "present both sides" of the argument is a cop-out at best, and deliberate deception at worst. Consider how you'd react if your school decided to present "both sides" of World War II, and invited the Institute for Historical Review in to give a seminar to the pupils. Sometimes there's a good reason why proponents of an established doctrine are arrayed against those with a different point of view.
All of these topics have a common theme, which is "how do we know what we know", and "how do we decide what to believe."
Most people seem to take positions on any number of matters, not because of having examined the facts, or the arguments for and against, but based on how compatible these positions are with core beliefs and prejudices. An example you gave is the reaction the astronomical community had to the notion of an expanding universe.
Your explanation for the opposition was an emotional rejection of the very idea that the universe might have had a beginning, and therefore might have a creator. I can think of another explanation, namely that astronomers were still wedded to Aristotle's notions of a perfect, unchanging universe. (Einstein, confronted with an expanding universe implied in his own equations, added a "fudge factor" to make the universe stationary. He later described this as the worst blunder of his career.)
However, one thing I would like to call to your attention: the big bang theory is now the reigning doctrine in astronomy. Nobody proposes going back to the steady state theory to avoid the possibility of the universe having had a beginning.
Why was the big bang theory accepted, despite initial opposition? Because the overwhelming weight of evidence was in its favor. Once people knew what to look for, they found that all the evidence pointed to an expanding universe.
As you know, the Fox network presented a video making the case that the Moon landings were faked. The program made a case which is superficially very compelling, but only because all the evidence showing the landings were real was excluded, and the few facts that made it on film were heavily reinterpreted to support the hoax theory.
When you stop and examine the issue, though, the evidence that the moon landings were real is so solid, and from so many different sources, that it's perverse to continue to discount it. Provided, of course, you accept the sources as authoritative. If you happen to believe that the government is engaged in a vast conspiracy to pull the wool over all our eyes, you might decide that every source except for this one video is lying.
The issue is very simple. The moon landings happened, or they didn't. There is no in-between. But who has the time, or the energy, or the ability, to check out all the claims and counter-claims?
The same questions apply to the subject of evolution. Again, as a statement of objective fact, either all life is descended from a single ancestral organism, or it isn't. Either the first living thing arose through natural processes, or it didn't. Either life as we know it came to be the way it is through processes found in nature, or it didn't.
Support for evolution, and opposition to "creation science" is sometimes due to opposition to religion, to ascribe all support for evolution to anti-theist sentiments is to slander the millions of evolutionary biologists who are devout, believing Christians, Jews, Moslems, etc. Many, indeed most, believers are perfectly content to believe in a God who created the rules of the universe such that their blind, mechanistic functioning would have been designed to give rise to life and all the complexity we see around us today.
Indeed, the antipathy to evolution that I see in "creation scientists" and "intelligent design theorists" is just as telling in its own way as the rabid anti-theism of people like Richard Dawkins. It seems almost as if the anti-evolution crowd is terrified of science. They fear that as scientific discoveries reveal the natural causes of everything around us, their reasons to believe will be annihilated.
When Darwin proposed his ideas, the entire scientific establishment believed that life came to exist through special creation. The diversity of life and the intricate order of nature were seen as the result of the divine hand. Biology's place was to examine the natural order and learn what God had in mind when He was creating the world. (Back when science was called "natural philosophy", scientists felt they were learning the mind of God from His creation.)
What about all the problems with evolution?
When Darwin first proposed his ideas, special creation was the dominant belief. Darwin's singular idea was not just the idea of natural selection, although that is a major idea. His major idea was the notion that processes that could be observed in nature were sufficient to explain the diversity of living things. This idea has been expanded over time, and the current doctrine holds that processes that can be observed in nature are sufficient to explain the origin of life itself.
From the very first, many people elucidated what they saw as problems with the theory. A famous argument is known as "Paley's watch argument". If you saw a pocket watch on the beach, the argument runs, you'd immediately recognize it as a manufactured thing. The simplest living thing is more complex than any watch, so it must be even more necessarily a designed thing.
The problem with this argument is twofold: Firstly, we have experience of watching people build watches, as well as a variety of other mechanical devices. Secondly, as research continues, we have accumulated experience of watching molecular systems, and even intricate molecular machines, self-assemble. The physical properties of molecules and their environment drive this self-assembly. Natural processes can accomplish a lot.
Nowadays, science finds that the processes that exist in nature are uniformly sufficient to explain everything around us, sooner or later. The problems Michael Behe expounded upon in his book, "Darwin's Black Box", have begun to fall to persistent investigation. The elaborate blood-clotting mechanism evolved from a much simpler one-step mechanism through gene duplication and subsequent differentiation of functions. The flagellum started out as an excretory system, and only later became useful for movement. I have no doubt that when the visual chain reaction is examined, it will prove to contain derivatives of proteins that exist elsewhere, in slightly modified forms.
Behe's likens the evolution by natural processes of the machinery of a cell to jumping across a mile-wide chasm. He represents naturalistic explanations as akin to claiming that stepping stones rose from the floor of the chasm long enough to allow a person to cross, and then retreated. In fact, what we see is that where now exists a chasm, there was once a bridge, and the bridge has since fallen down. After he calls our attention to the problem, we do the equivalent of shining a searchlight down the chasm, and what do we find? Pieces of a bridge scattered across the bottom. All of a sudden, the presence of people on the other side of the chasm is a lot less mysterious.
Can we prove that the mechanisms proposed for the development of vision, blood clotting, and so many other intricate systems are the ones that were actually used? No we can't. By the same token, in the example given in the last paragraph, we can't prove that the people on the other side of the chasm used the bridge whose pieces lay at the bottom. But the existence of the fragments of the bridge seriously weaken the need for the hand of God to carry people across this gap.
Often the claim is made that we need to present both sides of certain issues. Many who wish to teach creationism in public schools appeal to an "equal time" argument. It's only fair, they say, to give the other side a chance to present its case. But is it really fair to dump this sort of debate in the laps of schoolchildren before they've acquired the tools needed to sift through conflicting claims?
What if, instead of, say, the Creation Research Institute calling for equal time for creation, we saw the Institute for Historical Review (IHR) calling for equal time for its view of the Holocaust? Is it fair to ask school kids to come to their own decisions based on the IHR's presentation and however much time the school can bring to bear in rebuttal? If we bar the IHR from presenting its case in schools, they can certainly cry censorship. Do we give in and let them have their say? Or maybe we can take the approach so many schools have taken with evolution - skip the subject entirely.
Your brother uses the example of a person walking along, coming upon the rubble from a land slide, and finding a bunch of rocks that spell out the message, "hello, how are you?" If you saw something like that, you'd have to conclude that an intelligence was at work. As it happens, I've seen that countless times. In fact, there's a gravel pit near my home that has just such messages. All I have to do to prove it is remove all the rocks that aren't part of the message.
I'm only half kidding here. A lot of the basis of "intelligent design theory" is meaning assigned after the fact, and very bad estimates of odds for and against events.
Your brother's implied argument is that the development of life is equivalent to a number of rocks falling off the side of a mountain and landing so that they line up to form a message, and nowhere else. No serious student of evolutionary biology believes that scenario. The accepted scenario is much more like my example, where rocks have peppered the landscape, and some of them form a message. The problem lies in identifying what sort of selective mechanism will remove rocks that aren't part of a working message.
We don't know all the details yet, but if I were to place a bet on the outcome, I'd bet that a workable path from chemicals to living things will eventually be drawn without recourse to any supernatural forces.
Atheists will be comforted (?) by this lack of reliance on anything beyond the pale of nature; theists will be able to regard this as the result of an exquisitely designed system of laws.