I have a few pet peeves when it comes to instructors, coaches and sensei.
One of the more indidious and most damaging to the student is the " you (meaning the student) just don't GET it." implying that the student lacks the wherewithal or the ability to grasp either the concept or the physical movement the instructor is attempting to impart.
I have seen it time and time again. The general process is as follows. The instructor makes a statement of demonstrates a technique and the student fails to understand fully, fails to replicate the instructors movement or even worse dares to question the underlying foundation of the concept or the physical efficiency of the technique.
Such treasonous action is often met with the response, "You don't GET it" what the instructor/sensei or coach is really trying to say is, "Your ability is so far below my own that you have failed to understand." indicating that the teacher is operating at a level so far above the student or the outsider that a more detailed discussion is not required.
This is arrogance at best, at worst a deliberate attempt to derail the question mark over their teaching.
The corner-stone of all understanding is a questioning mentality. Not an accusatory one, a questioning one. As a student you should OWN your development. As an instructor you should be facilitating that mindset, not inhibiting it.
I firmly believe that the failure of any student to understand is the fault solely and exclusively of the instructor. There is a method for reaching everyone, a method for imparting information that works for everyone. The individual may learn best through listening, seeing, doing or replicating. It is your job to find out what method reaches them most effectively and aids their understanding.
Explain, do, explain while doing then have the student train the concept or technique under supervision.
It is perfectly acceptable for a student to say, "I don't understand" it is completely unacceptable for an instructor to say, "You don't understand."