I believe the proliferation of legal guns, and CCW permits are one of the reasons we are seeing crimes using guns go down. Society is not getting more polite, nor less aggressive, but criminals now legitimately feel they could come up against citizens legally defending themselves, and their homes with guns.
All the evidence points to a lower "proliferation" of guns in the US.
Notable crime drop has lots of reasons. A better and more often publicly armed and equipped citizenry may be one of them.