Kimio's point about prohibition is a good one.
However, it only goes halfway because it falls into the same trap many pro-gun arguments do: arguing from utility. Asserting that gun control won't reduce violence is only half of the story.
The primary issue is philosophical. Prohibition was supposed to make people better. It failed at that, as will any attempt to do so through laws or regulations. Millions who imbibed responsibly were punished for the acts of a few.
The same argument applies to gun control. I have a right to defend myself. That right has already existed. Locke and Blackstone spoke eloquently on it. The framers made sure it was protected with the force of law.
Bad people will do horrifying things, but penalizing the people who didn't do it isn't just, fair, or righteous in the least.
Sometimes it’s nice not to destroy the world for a change.