May I direct your attention to Aviation Instructor Handbook, page 7-7, figure 7-6. In the list of "Instructor Dont's" is the admonishment, "[Don't] disrespect the student." The tone of the characterizations that you've shared suggest a lack of respect for your student that seems unrelated to his parents' involvement.
In particular, the comment "...but he is also a marching band nerd" says much more about his instructor than it does about the student. After that revelation, it appears to me that the best solution is to pair the student with a different CFI--one less biased and judgmental--for the student's sake. Without knowing any more about you other than what you've posted here, you sorta remind me of a certain Alpha Male CFI who was involved in a
recent tragedy, which was the subject of this
insightful video.
Flying aircraft is neither an Alpha nor Beta environment--it is an environment to which a wide range of personality types can adapt and flourish, and one in which ALL personality types have to adapt, to flourish.
In the FWIW department: From my high school, I know of three band nerds who went on to fly professionally--two in the military and one civilian. All three ended-up at major airlines. Of the thousands of pilots that I flew with during my career, some of the very best were also active musicians who performed at a high level on stage and on the flight deck. Recently in the news, Daniel Harding, who holds a First Officer position with Air France, was named
Music Director of the LA Phil(!), succeeding the great Gustavo Dudamel. Maestro Daniel Harding: music nerd and former student pilot, who has reached the pinnacle achievement in one of the most hyper-competitive, hyper-demanding professions in existence, while also working as an airline pilot. So what, exactly, is the problem with "band nerds?"
Your student sounds like a kid who needs something that you are unable and/or unwilling to give. The best thing you can do is let him find a CFI who can and will provide the kind of instruction that he needs.