Srimad Bhagavatam Canto 10, Chapter 64, Text 41

SB 10.64.41

vipram krtagasam api
 naiva druhyata mamakah
ghnantam bahu sapantam va
 namas-kuruta nityasah
 
Translation: 
 
My dear followers, never treat a learned brahmana harshly, even if he has sinned. Even if he attacks you physically or repeatedly curses you, always continue to offer him obeisances.
 
Purport: 
 
Lord Krsna offers this instruction not only to His personal associates but to all those who claim to be followers of the Supreme Personality of Godhead.
 
Srimad Bhagavatam Canto 10, Chapter 64, Text 40
Srimad Bhagavatam Canto 10, Chapter 64, Text 42