The intent of the quote is that armed people know they are armed and thus avoid starting arguments and such.
An armed man walking around with a chip on his shoulder is the bad guy, and is screwing all of our rights.
Numerous episodes of Gunsmoke, The Rifleman, Bonanza, and Wagon Train explain this concept in Shakespearian detail.
Actually, you touch on why I was so confident, after the facts came out, that Martin started the fight with Zimmerman.
I would ask people this simple question: You have two men. One is a short, 30ish pudgy guy with a gun. The other is a tall, lanky guy who gets into fist fights for a hobby and recently lost a scheduled fight.
The two guys confront each other, resulting in a beatdown followed by a shooting. Question: Which guy started the fight?