"AN ARMED SOCIETY IS A POLITE SOCIETY"

((h/t Adam Gopnik)
That's one of the conservatives favorite slogans used to justify widespread gun ownership and as usual, it is FALSE.   In "Firearm availability and homicide: A review of the literature" by Lisa M Hepburn and David Hemenway, the authors come to this conclusion:

The available evidence is quite consistent. The few case control studies suggest that households with firearms are at higher risk for homicide, particularly firearm homicide. International cross-sectional studies of high-income countries find that in countries with more firearms, both men and women are at higher risk for homicide, particularly firearm homicide. This result is primarily due to the United States, which has the highest levels of household ownership of private firearms, the weakest gun control laws, and the highest homicide rates. Time series studies of particular cities and states, and for the United States as a whole, suggest a positive gun prevalence-homicide association. Finally, perhaps the strongest evidence comes from cross-sectional analyses of U.S. regions and states. Again, places with higher levels of gun ownership are places with higher homicide rates.

None of the studies can prove causation and none have completely eliminated the possibility that the association might be entirely due to reverse causation or omitted variables. But the available evidence is entirely inconsistent with the hypothesis that increased gun prevalence lowers the homicide rate. Instead, most studies, cross sectional or time series, international or domestic, are consistent with the hypothesis that higher levels of gun prevalence substantially increase the homicide rate.

You can find summaries of other research by David Hemenway here.