Plain and simple, restricting firearm ownership is not going to stop the gangbangers or the nut cases from killing innocent people. The only people affected by additional restrictions would be those people who abide by the law. The "bad guys" have always had guns. Do you really think banning automatic weapons or requiring registration is going to change that? These people don't buy their guns legally, so it's doubtful they would be registered unless they were stolen from a citizen who did buy them legally.
I don't own a gun, but I would think that if I were going to rob someone, I would be less inclined to do so if I knew they too were carrying a gun.
I'm not sure how I feel about concealed carry. On one side of the coin someone whose intent is to rob you wouldn't know if you have a gun and would have to be willing to take that chance. On the other side, if a weapon is visible, I would think the robber would be less inclined to attempt the robbery.