Captain's prerogative.. He's in charge. Its his call.
He didn't sacrifice a kitten on the FMC, he tossed out a security risk.
I would do it, WE have done it countless times with items left by ground staff, paperwork. Its a non story.. one the British media would rather play up than the fact your country is bankrupt and your aircraft carriers have no planes, or any number of other things the public should be concerned about.
Bloody Drivel...