Tilley, some other info you might find interesting,
http://en.wikipedia.org/wiki/Kennesaw,_Georgia#Gun_law
http://en.wikipedia.org/wiki/Gun_politics_in_Switzerland
Look at it this way, if you're a criminal and you have two identical places to rob, one being a place you can't carry and one being a place you can, the obvious choice is to rob the one with less threat - the one where carry is banned. If the chances of criminals having law abiding citizens shoot back increases, crime will decrease because the criminal might actually act like a logical human and say "hey, something bad might happen if I try this".