James Holmes and Gun Control

The NRA tells us that "guns don't kill people, people kill people." This is obvious. But it completely misses the target. People with guns can and do kill more people than they could without them. We've learned that James Holmes had an AR-15 assault rifle with a 100-round drum magazine. It could fire 50 to 60 rounds per minute in quick succession, a video of it can be seen below. While it seems no one could foresee his killing rampage in that Colorado theater, there is no reason this weapon or any like it should be sold in gun stores. Luckily it happened to jam on him. While it's true that the criminal mind can find such guns on the black market, there is no good reason they should be produced or sold legally. None. Give me one good reason. Just one. The issue I'm raising is not how to interpret the 2nd Amendment. The issue is why shouldn't the production and sale of these guns be banned? I think they should.