Trying to point the presuppositions of someone who considers themselves completely objective or rational is a lost cause, I've found. They quickly fall into circular logic, but fail to see the circularity.
The objectivity I claim does not reside in the dogmatic axioms, they are indeed unproven, the objectivity is in the fact that a some theorem provably follows from the axioms.
I state nothing less myself when I describe "fundamentalism" as a better moniker: the quest for locally minimal sets of axioms that allow maximal sets of theorems to follow from them without generating mathematical inconsistency.