When people argue against assault rifles, as an example, 'because they aren't necessary for hunting' - its a straw man argument. Hunting was never the reason for the second amendment.
America was a country that had to earn its independence. Early americans wanted to preserve the right to form militia, or to defend oneself from hostiles (who themselves might have access to guns), or from invaders, or from their own government. You know - the people shouldn't be afraid of their government, the government should be afraid of its people.
Making guns illegal is all fine, until the day a tyrant gets hold of your government and turns such forces as the police force/military into enforcers of said tyranny. Hopefully you'll never need to use your right to bear arms to throw off a tyrant. Or if someone w/a fascist bent manages to get elected in your country (whatever that may be) the fact that you and all the other citizens are armed - will certainly limit how far he'll be able to go while he remains in control.
besides, guns are very simple low-tech devices, you could make one in your garage w/completely legal machines/materials. Certaintly not on par w/modernized military special weapons, but they'd do the job. Making them illegal would no more get rid of them than making meth illegal does, unless you could also get rid of the *demand* for them so no one felt it was worthwhile to produce them.
Look at how some of the martial arts were born, when weapon ownership was made illegal for the peasants, so they created fighting styles that turned their farm implements into equally as deadly weapons as the ones they weren't allowed to own.