Some of this is simply common sense ....... has nothing to do with the 2nd ammendmant
Very little of your argument is common sense. Unless you're talking the same thing as liberal "common sense" gun laws.
To restate the facts of this case:
Store was locked.
Back room was locked.
Guns were in back room.
Bad guys stole SUV (felony - grand theft auto)
Broke and entered store (felony)
Stole multiple thousands of inventory (grand theft - another felony)
They drove said SUV through two walls (the correct two walls to gain access), which means they KNEW what they had to do to access the guns. What makes you think that if they had been in a safe they wouldn't have brought a torch?!?!?
They did NOT leave guns in plain view behind an unlocked door; which some of your statements seem to be implying this was analogous to.
NEXT:
As a private citizen owning a gun, do I have a legal responsibility to secure my firearms? No.
Do I have an ethical duty to secure them? I would say yes.
What/who defines "secure" is the question. It has not been legally defined (there's no legal duty to do so, so I don't expect it to be defined). And you have no legal OR ethical authority with which you can claim to define it for me.
So, if you think "secure" means inside a safe, inside a vault, inside a dungeon, inside a castle, inside a moat, with a drawbridge; then by all means, do so. But that does NOT make it required for me or anyone else.
Calling your definition "common sense" is no more reasonable than calling assault weapons bans "common sense" or standard capacity mag bans "common sense". In fact, it is precisely the exact same argument made by liberal gun-grabbers. You have literally made "it's for the children" and "but my definition is common sense" your argument in this thread.
In short, inside a locked house IS a valid definition of "secure" in this context. Maybe that doesn't give you the warm fuzzies, but that's not my concern.