They always use the example of Korah and Moses with this. They fail to see that that they are Korah, not us.
Korah challenges the authority of Moses despite all the evidence that YHWH was using him (miracles etc.). Moses never got it wrong. Moses didnt flip-flop.
Do we see any evidence that YHWH is using the GB? No. Did Korah have any evidence that YHWH would choose him? No. Both Korah and the GB assume a position that is not theirs.