A good instructor is one that can adapt his/her teaching methods to meet the needs of a student. Arrogance has no place in a cockpit, be it a PA38/C172 or a B737 etc.. generally it is the sign of someone that thinks they know it all when really we are all students of aviation, whether we be a seasoned airline pilot with many thousands of hours or someone that has been flying GA for many years.
I too prefer a more informal approach to teaching PPL students, epaulettes on instructors seems a bit over the top for my liking.