.... Please hear me out before getting out the flame-throwers ..... I'm not sure that pilots having guns is the greatest idea in the world.
I know they're trained and I certainly wouldn't have a problem with trust ..... my gosh, you're already putting your life in their hands when you get on the plane .....
But if there is a chaotic situation on board a flight (which there would be if there was a question of the pilot needing a gun), I think I'd rather the pilot was giving all his attention to the controls.
Far better, IMO, to have armed marshalls or every flight ..... or let those with CC permits carry their weapons on board. Then no one would get far enough that the pilot would need to use a gun.