Did you really not read the post I was responding to? That's sort of how forums like these work, they're not just random remarks without context. In fact, someone DID bring up bats and clubs.
Yes, I did. Well, sort of. I asked the question of alasdairm, but it was meant in a broader context. If someone intends you harm, or more aptly death, you have a few options. Flee. Call for help. Self defense. That's basically it.
Fleeing is situation specific. You may or may not have the option.
Calling for help (i.e. police) has an element of time. You may or may not have enough.
Self Defense is the most direct method. It has no time constraint and can always be attempted (you always have the option, even if you ultimately fail).
My example of the lessor weapon is merely to illustrate that in self defense, equal or greater armament at least removes a disadvantage. If someone attacks you with a bat, a knife may be sufficient because it can inflict a greater wound with less effort. But what of guns? The only sure counter to a fast-moving ranged projectile is another fast-moving ranged projectile. Melee weapons are possible, but are clearly at a disadvantage. (We're talking in the civilian sense here, so no need for "BUT NUCLEAR WEAPONS!" or other hyperbole.)
So in as much as people want to mock the statement "The only thing that stops a bad gun with a gun is a good gun with a gun," because it kind of sounds silly/ridiculous, it's actually 100% true. If we choose as a society to allow private ownership of firearms, then we must also accept the reality that we will need designated "good guys" to also be armed. Equal force for self defense. Some would consider the police to be the designated group, though I guess it depends on your point of view. (I'll leave that argument for another time.) But again we're back to that element of time. So what other option is there but to allow civilians to carry as well? If we don't we must collectively accept that when an incident like this occurs, some of us will be sacrificed before "help" arrives.