Imam Abdul Wahab Sha’rani (R) writes: A covenant was made with us (Muslims) on behalf of Rasulullah (Sallallahu-Alaihi-wasallam) that we respect the Ulama, the saintly and the elders, whether they themselves act according to their knowledge or not. And that we shall continue to discharge their necessary rights and entrust their personal matter to Allah Ta’ala.
Whosoever fails to discharge the Ulama’s rights and fails to show them the necessary respect and honor is indeed guilty of sin towards Allah and His Rasul (Sallallahu-Alaihi-wasallam), for the Ulama are the successors of the Ambiya (AS), the heirs of Rasulullah (Sallallahu-Alaihi-wasallam), the bearers of the Shariah and they are His servants. When anyone insults them, the insults set forth a chain reaction which reaches Rasulullah (Sallallahu-Alaihi-wasallam).
This is Kufr.
Now think for yourself: The king appoints someone as his ambassador. The king will with attention listen to this ambassador and debar the insulter from his court. On the other hand, the king will make a favorite out of that man who showed respect and honor to his ambassador and who discharged the rights due to his emissary.
(al-I’tidaal of H.Sheikh)