I don't think it is mean to question the crew. I asked a Cabin Manager a couple of days ago what the purpose of being in the flight deck was. She thought it was to keep an eye on me, she wasn't sure what she was watching out for
. The point is that the Cabin Crew have NOT received any guidance on what they are actually doing in the flight deck. I then went on to ask what she would do if I told her that I was going to lock the FO out as I wasn't happy with his behaviour, she said that she guessed that would be o.k., she changed her mind when I asked if she would then be happy if I started descending to divert the aircraft. It was a very valuable conversation because it has caused her to have a good think about the potential situations she could find herself and it showed me that the current policy is a total joke and there for public comfort only. At that time she is now authorised to be the most important person on the aircraft as the company expects that she should over rule the CAPTAIN and open the door if she thinks it is not right.