The key here is the number SEVEN, as in SEVEN HOURS. If JetBlue couldn't find a way to deplane those passengers after SEVEN HOURS, then heck yeah they deserve to be fined. SEVEN HOURS constitutes an emergency in my mind (as well as probably most of those passengers) in that sanitation facilities were unavailable and food and water were depleted. If this were another type emergency, if the aircraft were on fire for instance, would SEVEN HOURS to deplane be considered an adequate response?
Of course not.
In an emergency situation, you do what you have to do to get those passengers off the plane. Period. If that means deploying the slides, you do it. What you do NOT do is wait until you have TWO MEDICAL EMERGENCIES before taking action—a paraplegic whose legs were immobilized long enough to constitute danger of thrombosis, and a diabetic who needs food every few hours to control their insulin levels.
Had somebody died, this would very possibly constitute negligent homicide.