Well you accept the fact that tanks aren't legal to possess individually in any way, right? You say it's because they aren't popular (for any reason, price,etc.). I say that it's because a tank is not an "arm". It can't be brought in your arms, so even technically it's not an "arm". Technically it's an engine of war or vehicule of war or whatever you want to call it except "arm". So imagine this: let's say people can legally buy machine guns, and they decide it would be well within their rights to affix one to their cars. Cars are legal to own, machine guns are legal to own, so there's no problem, right? As long as it's "popular", it's okay right? WRONG. The second amendment says you shall not infringe on the right to keep and bear arms, not the right to keep and bear (how would you "bear" a car anyway?) a machine gun mounted car. Why? Because this kind of car would be classified as an engine of war (and the first tanks were indeed armored cars mounted with machine guns).
If you've got it, then we can look at a closer analogy, an RPG (or a simple grenade if you prefer something more historically close). This is something you can bear on yourself, so it can potentially be called an "arm". It's popular with terrorists, and so it could become popular here since against a modern army it would serve a militia well. So then legalize it as being something the right of possession of should not be infringed. Then it becomes popular and you can't regulate it? And you have to wait until it becomes not so popular to regulate it? Popularity as a criterion for being an "arm" makes no sense. It makes no sense because if you can create a de facto shortage of what would otherwise be legally considered an "arm", you can make it illegal to obtain as being "not popular enough" to qualify. That's why the majority opinion says you can regulate the possession, but cannot ban the possession in whatsoever way. And this brings us to the case of the handgun ban of D.C. The only reason for the majority to bring the point of the popularity of handguns in D.C. is to show that the law retroactively makes criminals out of everyone that bought and still keeps a handgun, unless he renders said handgun uneffective for self-defense or other lawful uses inside his own individual property. This makes it as if he didn't effectively have an "arm" in his possession, only a simulacrum uneffective for actual lawful use, and this goes contrary to the spirit, if not the exact letter, of the second amendment, which says you shall not infringe the right to KEEP and BEAR arms. It doesn't say anything about BUY or EXCHANGE or BARTER. Of course, if you ban the sale of arms, de facto you can't keep and bear one either so this of kind extreme "regulation" would be unconstitutional too. Thus the simple fact that you cannot keep a handgun in working order without being branded a criminal, is already unconstitutional in the eyes of the majority. Also, the argument of popularity of the handgun serves to show how stupid it would be to even try to make the case that a handgun is somehow not an "arm". But this kind of "common sense" argument is weak, which is why they don't base their case solely on this: its simply a rhetorical device to make fun of the minority opinion. Even the Framers would have laughed their ass off.
By the way, don't try and convince me that guns are bad or whatnot, I'm not an NRA member nor do I own a gun. But the american constitution is what it is, and if you don't agree, abrogate the damn amendment and don't try to fuck around it with underhanded regulations that try to circumvent the second amendment in order to outright ban the lawful possession of arms or some types of arms (again it all depends on what falls under the category "arms", but as I've shown there is ample ground to judge a handgun as an arm without using a popularity argument: you just have to define the category "arms", either positively or negatively, with some other criteria).
