markflyer6580 I don't agree with your opinion that only the First Officer has the right to argue the point with the Captain. If I was flying with a Captain who was breaking the rules and insisting on breaking the rules then I as Cabin Crew would not have any problem with reporting him or voicing my opinion to him.
What if us Cabin Crew are relying on the First Officer to stand up to the Captain, but the First Officer was very green and too scared to stand up to the Captain? If the Captain was to allow a child into the flight deck and the First Officer kept his mouth shut, then not only would the Captain and Cabin Crew get into trouble, but also so would the First Officer.
The last line of defense on any passenger aircraft is the Cabin Crew and NOBODY gets into the flight deck on any aircraft I am working on UNLESS the aircraft is already on the ground.
Whilst the DFT rules might seem a bit severe to you, they are rules that we all have to follow in this country. You might think the DFT are a bunch of desk jockeys (which they most probably are) - but they are looking out for the safety of everyone, not just those in the aircraft but also those on the ground.
If you ever make it into the left hand seat, you will have to follow SOP's unless you have bloody good grounds to ignore them and unfortunately disobeying an SOP about aircraft security is not one you will easily talk yourself out of.
And please please please don't ever rely on the people in the terminal from stopping the bad guys or dangerous items getting on the aircraft - aircraft security is everyones business!