Robert Heinlein was a science fiction author, sometimes referred to as the "dean of American science fiction writers".
The quote "
An armed society is a polite society. Manners are good when one may have to back up his acts with his life." is from Heinlein's novel "Beyond This Horizon" that depicts a world in which genetic selection for increased health, longevity, and intelligence has become so widespread that the unmodified "control naturals" are a carefully managed and protected minority. Duels and the carrying of firearms are socially accepted ways of maintaining civility in public because this provides a method of killing off certain less desirable individuals.
"
An armed society is a polite society" is often cited by pro-gun groups in justifying the proposal of universal carrying of firearms, however, the context of this quote is almost always omitted, as we clearly see in your use of the quote,
@country_hick.
Hamilton Felix, the story's protagonist states:
"Well, in the first place an armed society is a polite society. Manners are good when one may have to back up his acts with his life. For me, politeness is a sine qua non of civilization. That’s a personal evaluation only. But gun-fighting has a strong biological use. We do not have enough things that kill off the weak and the stupid these days. But to stay alive as an armed citizen a man has to be either quick with his wits or with his hands, preferably both."
Obviously, if the reason for everyone carrying firearms is to kill off as many of the weak and the stupid as possible, then society is hardly being quite so "polite", is it?
So, the moral of the story here is that if you want to make a point about something in the real world by quoting someone, first educate yourself before quoting a fictional character in a speculative sci-fi novel.
Or, as
@Dashmellow pointed out, you can use the same words in your own context while properly attributing credit to the author, which is how us pro-firearm citizens use it. Not a thing wrong with that.
As in: When anyone could be armed, bad actors won't be messing about with people they would otherwise feel free to when they know that their potential victims are unarmed.
This summarizes the same principle I referred to in an earlier post, more eloquently stated by the late, great, Colonel Jeff Cooper: "If violent crime is to be curbed, it is only the intended victim who can do it. The felon does not fear the police, and he fears neither judge nor jury. Therefore what he must be taught to fear is his victim."
And of course, in the quote from Heinlein's character Felix, he's obviously totally ignoring the concept that I'm talking about, the fact that the "weak and stupid" may well themselves be armed so that they won't be preyed upon. The modern-day analog being law-abiding citizens who legally arm themselves for their own protection against those who fear no law.
While Heinlein was a sci-fi writer on his own level, he was also, like many of his contemporaries, a raging anti-gun figure, and would likely be classified as a socialist or liberal today.
His own statement on his politics: In a letter to Judith Merril in 1967 (never sent) he said, "As for libertarian, I've been one all my life, a radical one. You might use the term 'philosophical anarchist' or 'autarchist' about me, but 'libertarian' is easier to define and fits well enough." Note that "libertarian" is also less alarming than "anarchist." No doubt Heinlein knew that...
But I like the way he breaks down labels here, which I find most in line with the average freedom-loving American citizen: “Political tags — such as royalist, communist, democrat, populist, fascist, liberal, conservative, and so forth — are never basic criteria. The human race divides politically into those who want people to be controlled and those who have no such desire. The former are idealists acting from highest motives for the greatest good of the greatest number. The latter are surly curmudgeons, suspicious and lacking in altruism. But they are more comfortable neighbors than the other sort.”
Personally, the former I would identify as socialists, a political construct with idealism at it's core and which never, ever works in practice. And there's nothing more dangerous than a well-intentioned idealist, just ask anyone who'e even lived under socialist rule. I would also substitute "realist" for "curmudgeon."