Hi Dave,
While agree with you in principle it is difficult to avoid circular arguments when there is no contemporary textual evidence. The effective argument is "The shafts point at Orion. Orion was important in the funerary arrangements of pharaoh. We know this because the shafts point at Orion". In this case the lack of texts is vital - just because it is such an unusual position and because the shafts are unique.
The problem is that archaeological evidence is just as subject to interpretation as historical evidence. To take the shafts as an example we have some definite, factual, physical information about them in terms of the physical space they occupy within the pyramid. Unfortunately the shafts are not anywhere near straight. I am familiar with the arguments as to why this doesn't matter but the reality is that, to view the shafts as targetting stars, or asterisms, or whatever, one has to subjectively interpret their purpose.
At that stage what people generally end up doing is siding with the expert (or experts) that they find the most convincing. We make personal decisions based on our own biases (conscious or unconscious) and we select the view that best fits.
Generally the majority go with the orthodox view - ie the view that most experts in the field hold. Some do it through an examination of their arguments, others just because so many experts can't be wrong.
Others will always go with the unorthodox or heretic whatever they are saying. It's just the way they're made.
However, there has to be a middle ground where we just accept somethings are unknowns - and possibly unknowables. Do the shafts target particular stars? Maybe. The balance of evidence might even be in favour of that. However, believing that they do is not a factual position - it isn't a fact that the stars point at Orion's belt - what is a fact is that many eminent Egyptologists believe that they do.
There is nothing wrong with challenging the evidence that the concensus is built on - some would argue that any serious researcher should ALWAYS challenge every thing (although where that leaves cummulative knowledge who knows).
I know it's a grind when one is continuously asked to provide evidence that has been given before but it's just the down side of having an educated opinion, I suppose.
Pete
God is our guide! from field, from wave, From plough, from anvil, and from loom; We come, our country's rights to save, And speak a tyrant faction's doom: We raise the watch-word liberty; We will, we will,we will be free!