David comments below that he feels much safer in places where people carry guns and is therefore against any kind of gun control. Also, he comments that since guns are so ubiquitous there would be no way to get all the guns out the hands of the "bad guys."
My thoughts, in no particular order:
It is certainly true that there are a lot of guns around, and that getting them out of circulation would be a massive, probably multi-generational problem. However, all that means is that if we want to end gun violence, we ought to get crackin'
I think it is worth noting that a pistol-packing public is of small use against these mass shooters; they are almost all suicidal and take out their victims too quickly for anybody to respond before damage is done. Many victims are children; surely we were not expecting them to have guns?
Also, although this has not yet happened, even in pistol-packing parts of the country, it's easy to imagine that would-be heroes firing at a mass-shooter could kill bystanders in the fray (there's a reason police practice through their whole careers) and further the carnage.
While it will no doubt be true for a long time, even if we do get crackin', that bad guys will be able to obtain guns, it is also true that (1) at least some of these mass shooters, like the last one, seem to have "cracked" and done their violence without the kind of planning that it takes to get contraband, and (2) the fewer guns there are, and the more illegal they are, the more likely that the authorities will be alearted to a here-t0-fore law-abiding citizen bumbling around in the underworld trying to get a gun.
It seems that these mass shooters have a sense, not only of rage but of entitlement; they seem to think that using guns is a natural and reasonible thing for an angry person to do. That sense of entitlement would also be reduced. If only criminals had guns, people who considered themselves ordinary, law abiding citizens would be less likely to resort to them.
Finally, I certainly agree with Robin, that this epidemic of angry, violent men must be tackled with understanding and social interventions besides gun control if we are to al live well together in this increasingly small world.