I was raised with an understanding that "guns don't kill people ; people kill people".
We all make choices in life, wouldn't you think twice about robbing someone if you knew there was a chance they had a 9mm Nano in their pocket? 
Numbers don't lie...
Right-to-Carry 2012
41 RTC States – Violent Crime at 37-Year Low
Self-defense is a fundamental right. The U.S. constitution, the constitutions of 44 states, common law, and the laws of all states recognize the right to use arms in self-defense. RTC laws respect the right to self-defense by allowing individuals to carry firearms for protection.
"More RTC, less crime: Since 1991, when violent crime peaked in the U.S., 24 states have adopted “shall issue” laws, replacing laws that prohibited carrying or that issued carry permits on a very restrictive basis; many other federal, state, and local gun control laws have been eliminated or made less restrictive; and the number of privately-owned guns has risen by about 100 million.5 The numbers of gun owners and firearms, RTC states, and people carrying firearms for protection have risen to all-time highs. Through 2010, the nation’s murder rate has decreased 52 percent to a 47-year low, and the total violent crime rate has decreased 48 percent to a 37-year low.6 The FBI preliminarily has reported that violent crimes decreased another 6.4 percent in the first half of 2011, translating into a seven percent decrease in the total violent crime per capita rate.7"
