We don't all NEED guns, but the presence of legal firearms actually reduces the occurence of armed robbery and similar violent crime, as stated by the very article you presented, and confirmed in thousands of such studies. You don't rob a store if the owner has a sawed-off shotgun under the counter. Not a good plan at all.
And I repeat myself: murder rates per total population are virtually identical across the entire first-world-nations. Every one of them looses around 1 to 1.5 percent of the population to one method or another of homicide. Naturally, this isn't including war-time actions, suicides, or accidents.
The idea of us owning firearms is two-fold.
1: So we can protect ourselves, independant of law enforcement or other governmental powers. So that we don't become too reliant on a government that, like all governments, is fallable.
2: To make sure that we can protect ourselves FROM the government, should the need arise. Can't say it has arisen, but if only the armed forces owned weaponry, it could.
Both reasons were Thomas Jefferson's, and the man knew what he was doing.
