> Think about abuse in other contexts to put it in perspective. If a teacher in the middle of giving a homework assignment had said the same thing, would that be okay? What about a police officer who pulled someone over during a traffic stop? What about a customer at a drive thru saying this into the speaker?

Calling a group of people "DUMB DOLPHINS" on an email chain ... Inappropriate, un professional, dis-respectful all seem like a better way to characterize it.

Its like the reverse of when Prince Andrew described Jeffrey Epstein behavior as "Un-Becoming". There is probably a better way to characterize it.