See the title. Firstly, we're talking the gateway drug to Ayn Rand. And Ayn Rand is beyond fatuous crap. Heinlein has some redeeming qualities, whereas Ayn Rand specializes in telling pubescent pimply faced boys that the highest goal in life is to be a self centered asshole. Like they need encouragement in that.
But beyond that, the statement is demonstrably false. I thought of this post while I was listening to an NPR report on the way to work this morning about Afghanistan. Afghanistan is, not to put too fine a point on it, the NRA's wet dream of a society.
Damned near every Afghani has a gun, most of them have automatic weapons, and the majority of them either own or, in a pinch, could easily put their hands on a rocket launcher. Wayne LaPierre would LOVE it there. There are a lot of adjectives that leap to mind when thinking about Afghani society. Polite isn't high on the list. Polite isn't even ON the list.
Insular, tribal, violent, sectarian, vicious, dangerous. They are on the list. Polite? Nope. I'm not saying that Afghan society would be Nirvana without weapons. It wouldn't. Thousands of years of Afghan history make it the way it is. But Heinlein claims that the presence of a large number of weapon carriers makes a society polite. A priori, and regardless of culture. And he's wrong. What makes it worse is that he knew, or SHOULD have known, that he was wrong.
History is loaded with societies where an armed society is a violent society. The example Heinlein plainly had in mind is actually in contravention to his claim. The American West may have been "armed", but it requires rose-colored hindsight to consider it "polite". It was a lot more "Deadwood" than "How The West Was Won".
Here is what an armed society is: in thrall to the people most likely to use weapons to get their way. Most of whom are Ayn Rand's favorite type of person: sociopaths.
The fun part is, by carrying carbines to town hall meetings, conservatives are attempting to strongly imply they are the latter, whilst pretending to the fictional condition. Polite isn't what they're doing. Ask Tiller. Ask the kids at that Unitarian Church in Tennessee. Polite isn't on the agenda.