Originally Posted by
theprestige
...To really understand the effect of good guys with guns on bad guys with guns, we'd have to look at statistics having to do with how many times the two encountered each other, and what the outcomes were. ...
No.
The mere fear that there might be good guys with guns might convince bad guys to bring a gun themselves, and/or use it very nervously. Such an effect would drive up violent crime rate, regardless of whether or not a good guy with a gun is encountered.