Let’s take a time-out on the gun control rhetoric and talk practicality.
Liberals and progressives make a lot of the apparent success of draconian gun control in Australia (since 1996), the UK, and to a lesser extent, continental Europe (as well as Japan and much of Asia).
It seems to be true that in these countries, tighter gun control reduces common “ordinary” crime, and probably domestic violence and suicide. On the other hand, as we saw recently, some kinds of strict gun control may make ordinary citizens more vulnerable to determined terrorist attacks. Gun control did not stop asymmetric enemies or professional criminals from obtaining weapons.
So the idea that “good guys (or gals) with guns” might have reduced the death and injury toll in the Bataclan does have some traction. Perhaps a venue like that could have hired more professional, licensed security. But, then again, in western countries almost no major private concert, entertainment, sports, disco, or shopping venue allows weapons or wants to allow them. But a similar argument could hold against determined attacks on private residences or business spaces.
In the US, there are so many guns in private circulation that European-style (especially Britain’s) gun control isn’t feasible. But consistent background checks are reasonable (they don’t stop law-abiding citizens, including women, from being able to protect themselves at home), and the idea that this is an open door for government to come in and seize later sounds like something from the sovereign citizens’ movement. Stricter control of small entities “in the business of selling weapons” by making them do background checks sounds consistent, but could set up disturbing areas where downstream liability is an issue, like in Internet service.
And remember, some of the cities with the most disturbing ordinary crime problem are “blue state” places with stricter gun laws, like Chicago and Washington. One of the most disturbing aspects of crime in some areas, like the DC area, is that even though total rates may be down, the likelihood of people living and functioning in “safer neighborhoods” being attacked has increased. But inequality plays into that aspect, as inequality, unchecked, begets instability and destroys the motivation to play by the rules.
The different camps on the gun control debate come from non-contacting moral perspectives. While both liberals and conservatives are concerned about hyperindividualism and the decline of social capital, social conservatives believes that learning to provide for the needs of other people has to start at home and in the immediate community, even if that community as a whole lives by ideas that are flawed. So social conservatives believe in an inherent moral responsibility to “take care of thy own” even in post-catastrophe environments where the normal system has broken down (the “doomsday prepper” mentality).
The ideology of the 2nd Amendment debate cannot be reasonably extended to unconventional weapons. Imagine the risk if ordinary people could possess biotoxins, radioactive materials (I've wondered about Taylor Wilson's inventions -- Nov. 7, 2015) or even military flux weapons. But, unlike guns, there is no precedent that these have any real value in self-defense.