depreciate

To lessen in price or estimated value; to lower the worth of.

[…] which […] some over-severe philosophers may look upon fastidiously, or undervalue and depreciate.

To prove that the Americans ought not to be free, we are obliged to depreciate the value of freedom itself.

To decline in value over time.

To belittle or disparage.

They depreciated him because he was the youngest on the team.