I agree, there hasn't been much though go into some of the above posts.
First exactly what screening are police not subject too? At BAA airports they carry the same passes as everyone else. Unarmed Police are made to walk through metal detectors, however, whatever a Police officer is carring, be it an asp (extendable baton) cs/pepper gas or a firearm he is permitted to carry it. A member of the BAA security is not, so how are they going to remove it? Then what? call another police officer to collect it and promptly conficate it from him....fairly soon you would have the whole station sitting round being detained and even less security!
As I stated in the last post, police customs and immigration are vetted, to a far higher degree than airline staff, cleaners and airport workers. At some stage you have to trust that higher vetting and look to where the lightly threat comes from.
To be honest this thread smaks to me of envy because the control authorities are not under the control of comercial concerns.