I was also totally opposed to having Guns on the flightdeck.
I have changed my mind only because I couldn't stand the thought of having to make ATC aware that I had a (potential or real) hijacking or terrorist situation on board and while we are trying to deal with the situation (if that was possible) someone in a F-16 is lining up to shoot me down, because we happen to be heading in the general direction of a critical target. At least with a Gun I have one more very deadly means at my disposal to postpone meeting my maker.
I am not sure how this Gun issue can be handled safely, I'd hate to be the one supplying some a**hole with a gun due to inattention or negligence on my part, if that should happen, the F-16 scenario would be preferable.