That is unacceptably unprofessional. I would recommend you reconsider sending feedback about this experience to the CBP: https://help.cbp.gov/app/forms/complaint

I've at least received some acknowledgment when sending feedback through this channel, and the CBP representative I had provided feedback on was provided "additional training."

And in case anyone's wondering, sending in feedback had no impact on my ability to reliably use Global Entry, etc. (i.e. no retaliation or anything else of the sort).