If you mix people with guns, people will be killed. I posted that observation on a website. The responses I got were informative. They pointed out that the same argument applies to banning cars, although I didn't advocate banning guns. Guns and cars come with both benefits and costs.
My point is that, in each case, the costs and benefits are a package deal. Guns can be used for hunting to put food on your family's table, for target shooting with friends or to kill trespassers on your property or anyone who you feel is threatening you. Cars can be used to get to and from work, shopping and kids' soccer games, etc. To get these benefits, you really have to put up with a certain number of gun massacres and fatal car accidents. A lot of effort has been put into legislation in both cases to eliminate these costs, with dismal results.
This conclusion can be extended to other weapons like knives and baseball bats. Knives are useful for cutting food and opening packages; bats make it possible to get some exercise on Saturday mornings. Both items can be used to stab or bludgeon many people to death, and that cost is accepted in order to get the benefits. These are weaker arguments, though, because their death rates are much lower than guns or cars.
For guns, this is probably a reflection of the adage "Don't take a knife to a gun fight."