I believe most people are basically good. This is supported by the fact that of the hundreds of people I meet on a weekly basis, none yet have tried to rob me. (Talking physical "gimme your wallet" robbery, here.) Though many of them easily could, it just doesn't happen.
So which is the greater fear: That the rare bad seed will attack and you can't defend yourself; or that one of the multitude of basically good people, when newly armed, suddenly becomes a criminal? I believe the first is much more likely, but fear neither situation so much that I personally exercise my right to be armed. If I had to live in certain neighborhoods, though, that might change.
Thinking about this, I realized there a three situations where my thinking is roughly parallel: surveillence, gun control, and helmets. All three are limits on my personal freedom -- I accept the argument that pervasive surveillence infringes on my personal freedom, so Addison and I disagree on that point -- but with different secondary effects.
I'll tackle helmets first, because my position is most unambiguous. Helmet laws are intended to protect me from myself. I absolutely disagree with the intent. I should be free to risk my own safety in any way that doesn't affect other people. I don't accept that possible higher medical costs may be borne by society, as some studies indicate for every extra head injury as a result of not wearing a helmet, there is an extra DOA that would otherwise have been a head injury. (If we're going to do actuarial analysis, we have to include all the costs.) But, even though there is no helmet law here, in Ohio, or in my previous rsidence, California, I always wore one. Because I evaluated the risks and made my own choice.
Surveillence removes my sense of freedom, if not actual freedom. What I get in return is the (supposed) guarantee that the operators will protect me from harm, or at the least that many misdeeds will not be committed because the potential perpetrators will also know about the cameras. But then I have to trust the government and the police to be absolutley scrupulous in their use of the system, and to never use it to extend their power beyond what they already have. Needless to say, I don't trust the government that far, nor do I think I should.
Gun control -- or rather gun prohibition ("Gun control is hitting what you're aiming at.") -- is advocated in the supposition that I will be safer if no one has guns. Leaving aside the impossibility of totally removing guns from society, and completely ignoring that one of the purposes of the 2nd Ammendment was to allow the populace to protect themselves from the government, this still assumes that the police would be better able to protect me from unarmed (with guns) criminals than I would be to defend myself.
Most gun control advocates also point to the statistics of people who harm themselves with guns, or to children who gain access to them. All of these (that I have heard) have been cases of people improperly handling and storing guns. Yes, this happens, but not to me. If you want to play Russian roulette, or just store the gun under your bed, feel free.
You also point to the societal cost of the constant seige mentality. I live in the same world you do, but I don't have that mentality. I worked hard to get to a point where I can live in a fairly safe neighborhood. I know several of my neighbors have guns in their homes, but I'm not afraid of any of them. In fact, one of my neighbors shot two intruders in his home several years ago and there hasn't been a robbery on our street since then. Of course, that might also be because we have three police offiers living on our street, all of whom have weapons in their homes. I once lived on a military base, literally surrounded by weapons -- big ones, little ones, you name it. I never felt safer.
So if the only, or the main, argument against the right of individuals to carry guns is that some people are uncomfortable with the knowledge that someone they pass on the street may be carrying, I have to say that isn't compelling enough to convince me.