Being a psychologist, well versed in learning theory - the postulate that continued exposure will reduce the fear of firearms is an interesting one. The idea that sheer exposure will do this might find some support from desensitization and extinction therapies used for disorders such as phobia.
However, the OC extinction folks miss a crucial point. In the therapeutic use, the noxious stimulus is presented in a manner that is controlled and clearly will produce no harm to the client.
That is not the case with OC (and especially with Modern Sporting Arm (ahem) folks who wander around). There is no guarantee that this OC user is safe. Thus, there is no reason to extinguish the fear. Also, the drumbeat of media portrayals of rampages and other gun crime, through observation and vicarious learning will continue to make the gun a noxious stimulus.
Simple extinction models sound nice don't have sophisticated take on the principles involved.
All in all, OC has been a net negative in the social context of gun usage. Being a theoretical right is correct but pragmatic application can be deleterious. That one can open carry in rural areas doesn't mean that it will be seen as positive in more populated areas without a strong gun culture.