Diddley Dee:
I really do think this nonsense has gone on long enough. I have already suggested on a previous thread that you should name and shame the perpetrators of this childish behaviour. Until you do, nothing will ever change.
In the first instance, you need to address the Flight Operations Director of the company concerned. If that does not do the trick, then you should copy your complaint to the CAA.
There is no reason on earth why you and your colleaugues should have to put up with such infantile and unprofessional behaviour. You cannot reason with cretins.