The safest city in the U.S. is Kennesaw, Georgia (also listed as one of the top 10 living areas for families). Kennesaw requires every adult head of household to keep a home protection firearm, excepting those who have religious convictions against firearms. It has had the lowest homicide and violent crime rate of any incorporated area in the country since adopting the firearms requirement.
Unfortunately, academic theory fails in the face of a large, complex, state, particularly one with liberal criminal laws and reluctance to institutionalize the mentally damaged. The fact is that predators naturally gravitate to where the most helpless prey is, so we need to remember that an armed society is a polite society.