Alright. Here is how it goes.
Drugs: Illegal.
DUI: Illegal.
Killing People: Illegal.
Theft: Illegal.
I hear that people still do everything on this list. Does that mean we should just go ahead and make them legal since people do them anyway?
Defacto the matter is that laws will only limit the law abiding, not the criminals. Criminals will always be just that: Criminals.
I hear that rocks are also a very nice weapon for killing people, along with knifes, plastic bags, cars, crossbows, bats, and of the sort. You can't exactly kill 20+ people with a knife or a bat... No matter what you do, you will only be limiting the law abiding who are trying to get protection against the criminals. Just because people could still potentially get their hands on illegal guns doesn't mean we shouldn't make it harder. If they're much harder to obtain, less people who want to do bad will be able to get them. The point is, if you give an evil man a gun, he will use it for evil, whereas if you give a gun to a good man, he will use it for good. And how do you know if a man is "good" or "evil"? There's no clear cut line, and it's impossible to tell in many cases. These mass shooters are generally people with no criminal records... It is always the nut behind the wheel.
Don't ban guns. You might as well be signing a bill that could kill thousands. Personally I think that if people really want to have guns that badly, they should be allowed to have them, just not insanely fast ones that can kill tons of people in just a few seconds. If you have a gun that fires just 6 shots or whatever before you have to reload, that's plenty to stop one person who's attacking you.
EDIT: Whoa. My brother is a ninja.