In this instance yes you can say that concealed carry stopped a robbery. Whether it avoided or increased the amount of bodily damage done will never be known. The problem is that increasing the number of arms to guard against errant use of arms will end up in chronic escalation, will probably only provide a mild deterrent to criminals, will guarantee that criminals will wear armour and carry bigger guns which are all readily available, and in all likelihood will increase the likelihood of armed robbers shooting first simply to 'protect' themselves and lives will go on being lost. Where does the line get drawn. Surely de-escalation is a preferable route?
What if the result here had been two dead would -be robbers. Would the CC still be a good thing? Does someone deserve to be executed for robbery? Does the civilian with the CC want to have that on their conscience? All worth considering.
In b4 'well if you want to try and rob me you deserve to get killed'.