Of course libertarians are not much interested in evidence anyway, they just have an ideological agenda to run; but it seems pretty obvious to normal folk that an armed society is not primarily a more polite society (if it is more polite at all) - it's primarily a more dangerous society for getting shot.
And the thing that really strikes me about the last year or two of shooting tragedies in the US is how readily it's glossed over that it was legally purchased weapons that were involved the killing. I mean, doesn't that make it obvious that it doesn't matter that the buyer appears to be a "good guy" at the time of purchase: what matters is how the gun eventually comes to be used. In other words, the problem is the guns being everywhere.
A good article in The Guardian puts this all in perspective. Here are the crucial paragraphs:
The National Rifle Association likes to argue that criminals, or people intent on committing a crime, will obtain guns no matter what the law says. Among the 5,417 gun homicides in 2012 that the FBI assigns a circumstance to (3,438 are "unknown circumstances"), a mere 1,324 were committed in conjunction with another felony. Three times that (3,980) were committed by otherwise law-abiding citizens. Of that, over half (1,968) were the result of an argument that escalated fatally out of control.Stunning figures that for any sane person means we are very glad to live under Australian gun laws rather than American. Here's the final paragraph from the article:
To put it another way: otherwise unpremeditated murders, where people kill out of momentary rage, are the single most common type of gun homicide in America. More than gangland killings (822); more than murders committed during robberies (505) and drug deals (311) combined.
You keep a gun out of the argument, you will save lives. This is not hypothetical. A person may be intent on killing someone else, but it is simply harder to do with anything else. That's why forms of homicide other than guns account for only about a third of all homicides. Someone gets angry at someone else, they may reach for a weapon. If we make guns harder to get, by requiring a test for the license, or by banning handguns more broadly, the one at hand might be far less deadly. Like, say, popcorn.