I never said we need more guns. (I'm not the person you were originally replying to)
I was responding to the remark about assault riffles and giving a reason why a complete gun ban is a no go (in my opinion).
However, criminals are more likely to attack the helpless. This is why most shootings occur in "gun free" zones. They KNOW no law abiding citizen will be able to shoot back. These cowards tend to avoid areas where there is even a possibility that they could be retaliated against. So if legal guns are allowed, potential shooters know there is a possibility that someone might shoot back, and are less likely to attack. And while a good guy with a gun may or may not be able to help in an active shooter situation (stopping the shooter earlier in the attack, thus reducing the number of casualties, but not eliminating them), they certainly aren't going to exacerbate it by killing more innocent people. However someone hellbent on killing will still fing their gun on the black market (like addicts do with drugs).