Great question.
There really should be a word or short expression for this. It could cover many schools of belief in human history and across cultures.
What about "argument from extrapolation"? The more you choose to extrapolate from your initial (incorrect) premise, the more convinced you become of the truth of that premise... and therefore of the structure you are extrapolating from it.
But you ask for an expression for the process itself, rather than the mental process which causes it, and particularly in the face of increasing counter-evidence. What about "rampant extrapolatory heuristics", or even "extrapolatory panic"?