Only partly true. The stupid thing was having a loaded .22 rifle hanging on the wall.
If it is a handgun meant for home defense and is unlocked, loaded and hidden in a place only accessible to the owner then that is quite a different thing than stupid. IMO.
Thus the adage: "ALL guns are loaded."
I would bet that the owner of this particular rifle had removed the magazine and/or emptied all of the rounds out of the feed tube without checking the chamber.
That said, the gun did not jump off of the wall all by itself, nor did it pull its own trigger. "Negligent discharge of a firearm" is just that.
The fault is with the perp, not the owner and not the firearm.
You sir have obviously never had skunks and other vermin in your yard.