TyroPicard makes some cogent points but one that sticks out and is so true:
In general, low-flying is prohibited (I mean low, not 500'agl) because it is not as safe as medium or high-level flying.
Can you show us footage of a test pilot at Farnborough Airshow flying that low in an airliner? If that pass had been performed at said airshow the pilot would not have been given the opportunity to repeat it.
I do know that in the UK height limits are placed upon a pilot's display authorisation and I doubt any would be allowed to fly that low in that type of aircraft at an airshow and empty of passengers.
I am fortunate to count as friends and work colleagues numerous TPs and several pilots with display experience both civil and military. All with whom I have spoken are unanimous about the 'display' and the circumstances in which it was flown (i.e. with passengers) - it was misguided at best and inviting disaster at worst.