TPM's Josh Marshall, in a long post about being a "non-gun person," offers a particularly distilled summation of the problem with the pro-NRA argument about "good guys with guns" being the answer to pretty much everything:

"...guns are extremely efficient tools for killing people and people get weird and do stupid things."

Indeed.

There's a fine line between "good guy" and "bad guy," and crossing that line is as easy as pointing your gun in the wrong direction. Happens all the time.

People with guns kill people more easily than people with other things.

Camper van Beethoven had this good guy/bad guy stuff figured out 26 years ago, so enjoy:

A further point: all the talk of returning to the Wild West, everybody's totin' world makes me wonder if there's a reasonable analogy.

Best I can do is the old doctrine of "mutually assured destruction." Every analogy is limited, of course. But to entertain this one: If every country had a nuclear weapon, would the likelihood of a weapon being wrongly used go up or down?

Answer seems, to me, self-evident. I bet it will seem self-evident to those on the other side of this debate, but it would be nonetheless interesting to hear them argue it.