Re: If you disagree with your instructor's explanations...
I completely disagree with quite a few of my instructors.
I feel my judo instructor's tactics and opinions on ground work are flawed and simplistic for example. However, I can not argue with his tactics and techniques for throwing people.
If I see something I feel is crap, first I will test it myself, then failing any positive results, I will ask my instructor for clarification. At that point if I feel he is still wrong I wait until a private moment and I challenge him on that assertion. Not in a fight, but just by saying "I feel this (insert whatever here) as I understand it is incorrect and this is why. Then I explain why, siting examples of my practice, my understanding of the art, etc. IF he ever was offended by that, I would then quit.
Just because your instructor is wrong is no reason to have any issue with him. If your instructor refuses to admit he doesn't know or is wrong, then by all means get out!