Having one in the chamber is just as irresponsible as having one in and the thing cocked IMHO. In fact, why did the 'flying leatherneck' think it was acceptable to have the thing on board in the first place?
So, you would suggest that you may carry a weapon but not be ready to use it?
As for why he had it, you may remember 9-11 when suicidal thugs invaded a defenseless cockpit.