When I originally posted this, I was speaking in general- If you disagree with your instructor's explanations
(often, regularly, a majority of the time, etc.)
Some folks interpreted this as "If you EVER disagree, than why is he/she your instructor?"
I was going for the general statement to provoke thought and discussion, but some took it as very black/white unyielding commentary.
I apologize if I offended anyone, as that was not my goal.
BTW, I like Amir's point about differentiating between one's teacher
and a momentary instructor.