ASL: "disparage"

The word "disparage" means to "regard or represent as being of little worth."
(Source: disparage. (n.d.). In Oxford Dictionaries. Retrieved September 20, 2019, from http://oxforddictionaries.com/definition/english/disparage )
 

The word "disparage" also means "to speak of in a slighting or disrespectful way; belittle."
(Source: disparage. (n.d.). In American Heritage Dictionary of the English Language, 4th edition. Retrieved September 20, 2019, from http://www.yourdictionary.com/disparage ) 

While there is no specific ASL sign strongly and specifically associated with the English word "disparage" there are various ways to express the concept in sign language.  Here are some approaches:

CRITICIZE (harshly or repeatedly)

NOTHING-to-it / it-is-NOTHING / no big deal:

Notes:
There are other ways to sign "disparage."  The above examples are just a few of the many approaches.

Also see: CRITICIZE