Do not belittle anyone ever

al-Munaawii says in Faid al-Qadiir volume 5 page 380

It is befitting for a person not to belittle anyone. For how often it is that this person he belittles is more pure of heart, more righteous in deeds, and more sincere in intention. Without a doubt, belittling the slaves of Allaah leads to loss, humiliation, and shame.