I don't need a weapon to kill you
There is one fundamental thinking error through the whole topic:
If a pilot wants his plane wrecked and everybody dead, he doesn't need a knife or a gun to do it. He has the safety or otherwise of everybody on the plane in his hands - can run off the runway on T/O, hit short on landing, overstress the ship - as has been done by suicidal pilots in the past.
Nevertheless a security check makes sense - why? Because it can be, that someone smuggles a bomb into crew luggage or crew bags (this has been done too).
What should the screeners therefore be seeking in Crew effects? Devices which would destroy an aeroplane.
What should they not be seeking? Hand weapons, scissors and spanners!
The problem of the suicidal / extreme pilot - fortunately not a common one - is one which cannot be solved at the security check - but must be addressed throughout his career by the company.
It would be a big help if crews and security checkers alike perceived this and then can work together for security instead of getting up each others' noses.
FC.