Even if your kids know about gun safety and would never mess around with your guns, can you say the same for all their friends? You can't prevent kids telling their friends about their dad and how he is all bada$$ with his guns. We have had several gun fails where a friend, neighbor or relative kid was the one firing the gun.
What other country-- relatively low in violent crime and not actively at war, claiming to be modern and civilized-- allows so many people to have access to so many weapons? From a world perspective, it is crazy to even be discussing an 18th century era "right to own a gun" versus people hurt and killed by guns. What made sense in scattered homesteads on the frontier with no police force and no communications system is an insane policy for most communities in the US today.
The gun fails are the sad result of lots of normal people doing normal but stupid things with guns, like forgetting to unload it, forgetting that there were other people around, forgetting how powerful their gun is (can shoot through walls) and just plain forgetting it somewhere. It just seems way too easy to hurt or kill someone by accident. And that is a high cost for some people to have a psychological sense of safety and power.
I liken it to the people who think they need to drive a Hummer-- a tank-like vehicle designed for military use-- on city streets to feel safe and secure. Because they can.