Either the boy was standing for the flight or he was not.
If it was the latter FR should sue the Mail. If it was the former there should be an investigation into what is a serious breach of regulations and a serious threat to the safety of all passengers on board ( picture what happens a standing 16 year old in cast when you slam on the brakes at 140mph and imagine him hitting you in the back of the head ).
It would be reckless to allow any passenger to stand for flight and to be aware of this before departure and if true the Captain and the Senior could be in serious trouble.
However it is also likely that the Mail have taken a few comments and turned it into a story. If that is the case then I really hope FR use their lawyers in a useful manner for aviation for once.
As for the other comments. The nervous handwringing by FR defenders is pathetic. It is either the boys fault, his supervisors fault, security's fault or the ground handlers fault, anybody but those actually responsible when the doors close.
Just because Michael O'Leary has decided that an airline is not a service but merely a bully taking your lunch money does not make it so. This is a service industry no matter what he or his cronies think and we should be looking after our passengers, particularly injured children.