"We do not know that the territory is single-level. It is conceivable that it is not, and
the available evidence does not exclude the possibility."
The available evidence does not support the possibility either. Lack of evidence actually is a form of evidence...for the opposing argument. http://lesswrong.com/lw/ih/absence_of_evidence_is_evidence_of_absence/
"Just: There are patterns that exist in reality where we see "hands", and these patterns have something in common, but they are not fundamental."
Reality is the space in which we observe trends that either bear out or contradict our beliefs. Reality seems to bear out a pattern corresponding with hands. Hands, then, correspond to something true about reality (even if it is just probably true, the probability is a true statement of something real.) We are not privy to the knowledge of how many removes we are away from the true experience of hands, but it isn't clear how one could convincingly argue the non-existence of a hand-like pattern OR that the bottom level of the territory corresponding to hands is more complex than the map we represent them on.
Otherwise stated: I cannot exclude the idea of the Bible being an exact account of creation. I can, however, disregard it in light of the overwhelming evidence to the contrary. If I do not disregard it then I must consider it on equal grounds with all "accounts" of creation and concede the utter impossibility of making a decision. To me, it is not clear how a human brain could be capable of granting equal weight of truth to mutually exclusive possibilities without a bit of cognitive dissonance or intellectual dishonesty.
So when something is not excluded by the evidence, you may either a.) acknowledge the high degree of probability that the unsupported claim is false (rationality); b.) disregard the evidence and believe in it anyway (irrationality); c.) see who can make the most unintentionally ironic assertion about the lacunae in the evidence holding more weight than the evidence itself (arationality.)
I don't see any likelihood for the existence of evidence of reality contradicting itself (thereby becoming non-reality.) I can't even fathom what form that evidence might take. Therefore I call reality objective and work within it as if it were. I'm open to the possibility of this not being true, but a person telling me "it might not be true" is not enough to forestall my effort at evaluating the trends I seem to see.
Reality is that which subjectivists can say nothing new or interesting about.