I once heard an anti-gun friend say is that, in a perfect world, there would be no need for guns. Since a perfect world has to start somewhere, many people choose not to own a firearm, thereby making the world a little happier, a little safer. But have they? We can reasonably assume that this sort of person normally obeys laws and would be, typically, extremely safe with a firearm and loathe to use it. After all, s/he does not want to kill anyone. How does this person, the very definition of a responsible citizen, not having a gun make the world safer?
One common argument is that, by not owning a gun, no one can steal the gun from them, thereby keeping a gun off the streets. But let's be reasonable here: the chances of one's home being invaded are pretty slim. If guns are stored sufficiently safely, the chances of these firearms ending up on the street are far slimmer. A firearm in your house is far more likely to protect you than to be stolen, I would wager, though I have seen no statistics on that.
Not owning a gun to possibly help others unknown to you is weak altruism of the worst kind. By not owning a gun and being trained in its use to simply keep it out of the wrong hands is to give up a very real benefit (possibly one's very survival) for a slight chance at a benefit for someone unknown at an unknown time. This sort of altruism does not appear in nature for a reason: it is not stable. The bad guy with a gun always beats the good guy without one.
If one is truly concerned about items in the house that can be stolen and used for evil, one would have to take a long look at common items. Someone stabbed with a butcher knife is far more likely to die than someone who is shot once with a handgun. Magic markers and other inhaled chemicals kill teens every year. Stolen cars kill people every year as well. Baseball bats are potential weapons. These are all risks we are willing to live with. Why? A thing does not have to be designed for violence in order to be capable of it. If one is really concerned about goods stolen from them causing harm, then they should have nothing that is potentially dangerous or valuable (lest someone get hurt while trying to sell, buy, or reclaim stolen goods). I argue that the cost of a firearm (slight chance of theft or accident) is outweighed by the benefit of being able to defend one's self and family against an armed attacker. We generally consider all of these other, potentially-dangerous items necessary and so are willing to live with the risk. My point is that we should consider a means to self-defense just as necessary.
It is my position that it is not a right so much as a responsibility to own firearms and be well-trained and proficient in their use, in order that one can defend one's self and one's family, and to store the firearm(s) responsibly and safely. Those who do not own firearms as a conscious decision to try to make the world better and safer are contributing to the problem of violence in this country by allowing themselves to be potential victims.