It is the logical conclusion of your thought process. You said guns are designed to do nothing but kill, right? There are hundreds of millions of guns owned by ~ 100 million citizens, right? So if they are designed to kill humans, and we don't have 100's of millions of people getting shot, then clearly they are not being used per their designed intent, right?
Guns are designed to kill people and you know it. That doesn't mean that every Tom, Dick, and Harry is out there eager to use them to kill people - relatively speaking, only very few do...but that 'very few' kill thousands of people every year, and wound tens of thousands of people every year...which results in a great deal of taxpayer dollars to pay for the care of the victims.
Look, guy, mistakes by doctors and hospitals kill a lot more people than guns do...but such cases are the very small minority of cases that doctors and hospitals see.
By the logic of the anti-gun-control crowd, then, regulating doctors and hospitals because of the malpractice of a few is "punishing" the rest of the doctors and hospitals for the sins of those few. And regulations of cars and drivers is the punishment of the many for the sins of the few. And regulations of air travel and air passengers is the punishment of the many for the sins of the few.
If you'll check, very, very few liberals actually want gun bans - they're the ones out on the bleeding edge of the Left, just as the ones who think that the civilian public should be able to buy machine guns, rocket launchers, and Stinger missiles are out on the bleeding edge of the Right. What I want - and what most liberals want - isn't a total ban of firearms. What we want is (1) to keep firearms out of the hands of those who really, truly shouldn't have them, (2) we don't believe that the general public should be able to outgun the police, and (3) restrict assault weapons and extended magazines to the military where they belong - such simply don't belong in the civilian community.
These are common sense measures, and they help make life safer for people in every other first-world democracy (except for Switzerland, but they've got other gun-control measures that today's NRA (though not the NRA of fifteen years ago) would call tyrannical) safer. This is why no other first-world democracy has to have their elementary schools practice lockdown drills in case a guy with a gun is coming to kill them.
Just because the Constitution says something doesn't make that something holy. Remember, there's been several things in the Constitution that were flat wrong - it's not always applicable to the modern day.