Leverage
I just listened to this audio, the PIC initially threatened to declare emergency to get what he wanted. As a controller for the past 39 years, I would have tried to accommodate the request however my understanding would be that the only reason for the declaration of emergency was to get another runway. In the event this was the case, this would be a gross abuse of "emergency" status and should have been followed up on by FSDO.
Imagine if everyone declared emergency everytime they didn't get what they wanted. Total Chaos!