So the post about the OC'er having his gun taken away and killed with it apparently disproves your proof that OC deters crime? So now I raise you the Waffle House robbery attempt and call with the dead guy having his gun taken away from him.
This topic has been hashed and rehashed. A common low threat thug may be deterred by someone carrying a firearm. A person determined to commit a crime does not care and will commit said crime anyways with the person OC'ing being the first target/victim.
As has been stated a firearm introduced into some situations can go bad quickly but the fact remains that if everyone can see it the process tends to speeed up. If you OC you better have your head on a swivel and think about every little thing. Body positioning, your enviroment, your loved ones around you, people in general around you, the bad guys, the good guys it all comes into play.