On the other side of the fence, we have to wonder what kind of people you keep around, where it seems like a normal idea for everyone to possess a tool that has the only purpose of killing and maiming people (i.e. handguns). Imagine if everyone had torture racks, and nooses, and scalpals and iron maidens in their garage, but of course didn't use them because there's no need. That would be weird right? To many of us who live in places where guns are restricted, the very idea of owning a killing device is just a very perverted thought. "Why would you want a killing device in your house - that's creepy!"
Your turn to think very closely about something, now. No knee-jerk reactions, here, no blindly spouting the party line. Exactly why is it a bad idea for the "average person" to own a firearm? Are average people the ones who do bad things with them? Is it honestly your opinion that a full 50% of the population would use firearms to commit crimes or otherwise behave irresponsibly with a gun if they had one? Really? Yikes. I wonder what kind of people you keep around you, that you have that perception.
Yes, a farmer with a long centre-fire rifle is a different situation. His tool is built for the purpose of killing animals, of which humans are a form of, but the primary use isn't killing people. It can be used for that purpose, and it's an extremely dangerous tool, so if he's not crazy/creepy, he'd keep it disassembled and locked up when not in use.
Again, if you went around to someone's house and they had functional rifles lying out in the open, it would be a very weird and uncomfortable situation... like seeing someone smoking at the gas station.
This is what outsiders mean when we talk about the US's "gun culture". You guys have an entirely different layer of abstraction that you use to think about weapons -- like when Jack Thompson refers to video games as "murder simulators" and we just think he's crazy and disconnected, Jack (assuming he's genuine) is operating on a totally different wavelength.
To us, the question is never "why shouldn't we have guns?", but "why on earth would you want a murder tool?". It's just very weird to be so very comfortable about these things.
Likewise, in many countries, and a small number of US states, simply being in possession of a set of lock-picks legally makes you guilty of having criminal intent to use them. It's so creepy for a person (without reason) to posses a trespassing-tool, that people are ok with them simply not being allowed outside of their professional use, and jumping to criminal conclusions. Likewise again with large quantities of drugs, the law makes the assumption that a person with a kilogram of dope has the criminal intention to distribute it, even if in fact it's for personal use, and apparently the average person is ok with being creeped out by people with bricks of dope.
Back to what you were saying, it's not that 50% of people will abuse the tool, but that any % at all will. Even if it's 0.001%, that's a huge number of incidents when multiplied by the population of a nation.
To take it to the extreme, imagine that we could give every household a tsar bomba. Now, from every day experience with our sane community, there'd be no problem, as no one would ever detonate their bomb... but if there's even a single unhinged person out of 7 billion, then we're in for one hell of an incident. There are no downsides to not allowing everyone to own a WMD, and there's a huge positive (there's very, very few WMD incidents).
You have to draw the line somewhere (surely you don't think that citizens should be allowed to posses nukes?), and the point at which the line is drawn should logically be at the best cost/benefit point -- where people are not inconvenienced by the restrictions, but the benefits of them are greatest. Obviously we don't want to live in a prison state, where you have to go through the equivalent of airport security every day and eat with plastic cutlery, but we don't want madmen detonating nukes either.
To us, small arms are the logical extreme of where the line should be placed -- they can exist where there is a genuine need, but beyond that they should be restricted for the greater good.
If the only change was that the penalty of "armed robbery with a handgun" was doubled, but "armed robbery" of other sorts was unchanged, I don't see how the pro-guns lobby would be able to oppose it as usual... Surely they're advocates for responsible gun ownership, and condemn the criminal use of guns?
Maybe a partial solution would be to impose much harsher penalties on criminal uses of guns. That should at least discourage the less committed criminals, which frees up resources to tackle the hard-core bad guys, who would probably have guns no matter what the law says.
The US already does this to a small extent. For example, certain types of ammunition are illegal, and it can be a crime to make use of restricted ammunition in the course of committing a crime. So robbing a bank with FMJ rounds is one thing, but robbing a bank with explosive rounds will really increase your punishment.
I personally don't see that as a legitimate argument... It makes the assumption that the presence of guns prevents crime -- that if you're being mugged by a guy with a gun, that you can stop it by being in possession of your own gun. I don't believe this is at all true in the general case, so the argument is just a red herring to me.
The legitimate argument is: If you remove all the guns from the law-abiding citizens, how will they protect themselves from the law-breaking criminals (who have guns)? How will the gov't ensure that no one has guns? Citizen and criminal alike.
What I do not get is how removing guns will not reduce gun crime in the US.
How many mass shootings in the US have been stopped by an armed citizen, compared to an unarmed citizen, or an armed officer?
Even if having everyone carrying guns is effective at reducing gun crime (I feel silly just typing that...), this need would diminish over time as guns are removed. At the same time that this citizen-defence capacity is diminished, the availability of weapons to murderers is also diminished. An unhinged person can't walk into a grocery store and walk out with a gun, so the capability for defence drops along with the capability of attack.
The government ensures that no one has guns the same way they prohibit anything. They confiscate them when found, and enact punishments for possession. If you get an extra 10 years in jail for being caught with a gun, then you'd be much better off committing crimes with a different weapon. It's not worth the risk to go carrying a gun.
If you look at the UK for example, they don't have guns, but you've got to assume that criminal gangs can illegally import them into the country... so this should be a big problem, right? It's so much not a problem, that their beat cops don't even carry guns of their own. If there actually is an incident with a gun, then SWAT appears with more guns and armour.
Due to this, most of the "gun crime" (armed robberies, etc) in Australia are done with fake guns or replicas with blanks! Circumventing the prohibition is too expensive, and the punishments are too great (and the risk of accidentally shooting someone is also too great -- but that's another issue, the US's homicide rate in general is absurdly high).
Common criminals can't even afford to get their hands on guns (like with prohibition of anything, legal enforcement causes the prices to skyrocket) so it's mainly the large organized crime syndicates that use them criminally... and these guys only use them to kill each other. You're not going to get mugged on the street-corner by a kingpin.