I understand how the position of controlling handbaggage can "stress" some airline employees. But before threatening someone with a not-applicable financial levy, an agent should pay attention to the details. Throwing out financial amounts prior to having any real grasp on the individual situation is just over the top.

The agent's people skills need some work.

[I think the agent was annoyed from earlier when I requested a seat change on my connecting flight from a middle seat in coach to either a window or an aisle on a plane where the majority of seats were unassigned. I inquired why a Platinum was given a middle seat on a connecting flight when it was clear that the connecting flight's seats were mostly unassigned still.]