The Messenger of Allah (sal Allahu alaihi wa sallam) said: “It is part of glorifying Allah that you show respect to a gray-haired Muslim and also to one who teaches the Quran.” [Abu Dawud]
Allah (subhana wa ta’ala) has fixed a position of honour for the elderly and for the teachers of the Quran and He requires all Muslims to keep their esteem in mind.
Showing respect to a gray-haired Muslim and to teachers of the Quran is not only Islamic etiquette; Realize that by this behaviour you are actually glorifying and praising Allah (subhana wa ta’ala).
By the same token if you are disrespectful, short tempered or arrogant with an elderly Muslim or a teacher of the Quran your behavior is being recorded as being insulting towards Allah (subhana wa ta’ala).
It is not a small matter.