Do you see that little word "likely" in my original post? It's small, so you might have missed it, but it means that chances are greater than 50% that something happens. The implication is that the odds are less, and, in truth, much less, than 100%. Here, I'll use it in a sentence:
"It is likely that 923 is so adamant about limitations on gun rights that he can't think clearly about practical measures to reduce gun violence."
Answer me this: other consequences aside, do you think it is more or less likely that the killer would have killed 49 people and wounded 53 if just 10% of Pulse patrons had been carrying?
This post makes use of a huge number of unproven and unprovable assumptions, then piles on top of them unspoken assertions that are contradicted by data.
Let's leave aside for a moment the implications of a society where, at all times, at least 10% of the civilian populace is toting a deadly weapon, and the question of whether such a society is a place where normal people want to live, work, and raise children. Such a society has lost all faith in its fellow citizens and the ability of the government to keep the peace. I personally don't believe such a society is healthy, prosperous, or ideal.
I note that Junebug carefully stated "is it more or less likely that the
killer would have killed" the same number of people. Perhaps it is marginally less likely that the
killer would have killed as many, but it is entirely possible that the overall number of casualties would have been the same or greater due to friendly fire from people other than the killer. Other posters have already raised the very valid question of whether all these armed people are going to be accurate shooters, and how the citizen-heros and the responding police are to tell the "bad guy with a gun" from the "good guy with a gun". In the dark, while possibly intoxicated, in a crowded nightclub.
We can look to the recent Waco biker shooting for some evidence.
https://en.wikipedia.org/wiki/2015_Waco_shootout The Waco police have been very, very cagey about this event, and many people strongly suspect a cover up. This was in broad daylight, in the outdoors. Many accounts suggest that once gunfire erupted, the Waco police started firing more or less indiscriminately at anyone who looked like a biker. There were "good guy" bikers who carried weapons for self-defense, they were targets just the same as the "bad guy" bikers. This was the supposedly highly trained Waco SWAT unit, and it is very possible that they killed or wounded a majority of the victims. Gun advocates always display great confidence in the ability of civilians in chaotic environments to pick off the "bad guy" with video-game precision. The evidence suggests otherwise.
Further, guns and gun policy do not operate in a vacuum. Increasing the gun carry percentage to some arbitrary number, say 10%, has knock-on effects that are entirely separate from mass shooter incidents. Mass shooter incidents are, thankfully, relatively rare. The Waco incident demonstrates what can happen in an environment where a large percentage of people are armed with deadly weapons - disrespect leads to gunfire, and then it's real hard to tell who the "bad guy" is. The fact that the US already has more guns than any other country by orders of magnitude, and also has more gun deaths by an order of magnitude, is extremely strong evidence that large numbers of guns increase gun deaths.
This basic fact gives the lie to the assertion that more guns would have a deterrent effect on these mass shooters. This is already the most heavily armed society in the world, and we have the most mass shootings. How much more heavily armed do we have to be to stop them? The answer from the gun absolutists is always "more guns" but common sense, history, and basic logic tell us that a populace armed to the teeth is not a peaceful or harmonious society. Plentiful evidence from around the western world shows clearly that less guns = less mass shootings. That's data. The assertion that more armed civilians is the solution is, at best, a fantasy based on wishful thinking about the efficacy of civilian shooters in a crisis, and at worst, flatly contradicted by the evidence of the rest of the world.
Finally, the post makes the assumption that if just this one variable changed and everything else remained the same, the outcome would have been different. Perhaps so. But the world doesn't work that way. Ask yourself, if a mass shooter wanted to attack a nightclub filled with armed civilians, would he come in dressed in paramilitary fatigues with a rifle and make himself the most obvious target? Or would he, perhaps, come in dressed like a clubber and armed with the same weapon as the clubbers, hoping to start a panicked shootout with lots of casualties? Or would the shooter simply escalate his choice of firearm or switch to those explosives that (we hear from facebook) are so easy to make and will be the weapon of choice if guns are banned? Maybe he'd just pour gasoline at the exits and light the place on fire. Or - and this is the most likely - the shooter would just pick a softer target. There is
always a softer target. Security and civilian armament measures extensive enough to put plentiful guns at every site where large numbers of people congregate would change our society to something completely unrecognizable.
TL;DR - it's a crock of shit, and a massive deflection from the real problem. Which is that there are too many guns in America, they are too easy to get, and all the "solutions" put forward by gun absolutists fly in the face of real world evidence and common sense.