I changed a bit, to make a point.
You consider the gun to have been "unwisely" (though not unlawfully) stored. The poor bastid in Lowell who was robbed had his stuff in a "Very secure" vault, and is jammed up by the PD.
If there are safe storage laws, then whether a gun owner is in compliance with them is the only "real" factor.
My point? No matter how secure it is, it can be defeated. If a criminal decides to steal then it's not the victim's fault. If the car was locked, would that have satisfied you WRT reasonalble measures? How about if the case were secured to the car by a cable, and it was cut? What if all of the above, and the car was in a garage, but the garage was closed, but unlocked? How about locked?
The guy complied with the letter of the law. Could more have been done? Sure. But you can ALWAYS do more!
The only ammo that I see here is "the storage laws need to be made more stringent, as even gun owners agree that the current ones let people steal guns."