I think that while a relationship between a teacher and a student can be inappropriate, I think that is certainly a rare thing. Teachers often have good strong relationships with their best students. Many of these relationships last for many years and progress more into a mentor type connection instead of just another school teacher.
Also if this student was being groomed for Drum Major then that is a different level of engagement between the band teacher and student. It would be the equivalent of a football coach and his star quarterback. So you can imagine if next year's starting quarterback joined a cult and quit football what the reaction might be from the coach.
Anyhow, good for him speaking his mind in a controlled intelligent way. I don't know if I will be able to stomach this video if it is being played at the convention.