Some 5 years ago I was flying QF BNE-CNS and had picked a seat in the back row /aisle on the assumption that there is often greater chance of an unoccupied adjacent seat. Just before I boarded at the gate there was a PA call for me to go to the service desk. Without any explanation I was handed a boarding pass to another aisle seat. I asked why I was being moved and was told that I was not permitted to sit next to unaccompanied children.
This is straight out discrimination against a solo male traveller. You are presumed to be someone who cannot be trusted near children, even though there are several cabin crew based at the rear of the aircraft only a few metres away. The experience was so demeaning that I would have walked to the other end of the terminal and rebooked onto VA had I not checked in a bag.
I spoke to the cabin crew and they were great - moved me to an aisle seat to the front of the cabin after take off where there was an unoccupied adjacent seat and provided excellent in flight service with a few beers to enjoy the flight.
The service agent had been entirely unhelpful - she had the option to seat me in an aisle seat with an adjacent spare seat (as the cabin crew had done) and made no effort.
IIRC there was a case where a male passenger successfully sued BA in a UK county court for discrimination and BA has subsequently ceased offering a service for unaccompanied minors. In that case the passenger was travelling with his wife!
It is sad state of affairs that you are presumed to be a pedophile simply because of your gender.
But perhaps not surprising when society fails to weed out child abusers in its midst (for example, Broken Rites estimates 1 in 5 Catholic priests are child abusers hiding under the cloak of "religious freedom": for instance in one case Father Michael McArdle reportedly confessing 1500 times and never reported to the Police).