There appears to be more to this one than meets the eye.
In a typically confused Daily Mail report (where do they get those idiot journalists from?) it's unclear whether the passenger going to the toilet caused the flight to miss its takeoff slot (i.e. because the cabin wasn't secure when it got to the head of the holding queue) or whether they just decided to return to the gate to make an example of the passenger.
Either way, getting on a flight with less than 30 minutes bladder endurance isn't a great idea.