there are several good points brought up here;
1) the guy next door has a gun, so if he loses the plot i can defend my-self. maybe he's thinking the same thing?
2) human kind has killed each other since we came down from the trees. all animals do this even cows that eat grass, lets face it, grass lives, it grows, it pro-creates so if a cow can eat grass to the roots so that it can no longer grow isn't that the same thing? remember, we mow our lawns or dig-up fields to build houses on, there are no innocents!
3) if you have a gun and i have a gun and we get into a real bad argument we may trade blows. if you get the better of me, i might well run into my house get the gun and shoot you down in my fear and temper. i'm still holding the gun when your family come out with your gun and shoot me down.
by tommydone's reasoning, his family then has to protect it self from the SWAT team that will turn up. but these are well trained marksmen that may kill your whole family. this is how wars began in prehistory. question; why would you need to defend yourselves against your own police and military. the USA is supposed to be the most enlightened country in the world. it seems it is also the most suspicious of it's neighbours and itself. we all watch American TV programmes, which is why the most of the rest of the world hate guns and what they stand for.
4) as twangtown, and my friend arkady point out, our police don't carry guns. you cannot buy a gun over the counter. the police only carry guns when they are called to an armed incident (or since 9/11) at airports. if you want to buy a gun, you have to have a damn good reason, pass mental and environmental checks, be a farmer and/or be a member of a gun club, which means you cannot take the gun from that club. and even with a licence, you have to renew it every year (i think) or so.
i am by no means saying that our system is any better or safer than the US, but violence breeds violence. once upon a time, we Europeans carried guns and swords, some countries police still carry guns, but i think (AND THIS IS JUST MY OPINION) guns breed fear, fear that the guy next to you has a gun and if you don't shoot him, he will shoot you. ergo; NOTHING GOOD CAN EVER COME OF A GUN.