Leaving aside the troll's incoherent points,
John Lott is probably one of the more careful researchers in the field along with Gary Kleck who is trying to accurately measure the impact of armed citizens on crime rates. I often see the tired maxim--correlation is not causation which is not an appropriate criticism for what Lott's studies have been attempting to do. Since direct experiments putting criminals and armed citizens ( I am purposefully not including criminals as armed citizens here) together under controlled circumstances is not possible, social scientists are forced to use regression studies using control variables attempts to determine causal relationships. A more appropriate criticism of Lott's studies might be that an ecological fallacy exists--what is true at the macro level of society is not true for the individual etc. Another might be that Lott actually understates the effectiveness of armed citizens in reducing crime because one cannot measure using his approach potential crimes that were thwarted by defensive gun use by the armed citizen. Often these are not reported to the police because the potential criminal act was disrupted by the presence of an armed potential victim.
One thing though can be said to be proved as much as anything is in policy research about armed citizenry is that society-wide, no credible research has been produced that shows an increase in armed citizens with CCW's produces more crime.
Gary Kleck's work using individual responses seems to indicate that defensive gun use (dgu) is quite extensive with even hostile researchers quibbling about the range of dgu use rather than denying it exists. Thus, a range from 800,0000 to over 2 million of defensive gun use by individuals per YEAR is implied depending on imputing survey responses to the annual National Criminal Victimization Survey (90,000 households composing of nearly 160,000 individuals) to the national population. Now dgu is simply defined as anything--e.g. a potential victim verbally or pantomiming a warning a possible criminal that they are armed (even if not true if I remember correctly) up to using lethal force. This seems to rule out that an ecological fallacy exists as Kleck's findings at the individual level indicate support for Lott's conclusions.
Small scale evidence that an armed citizen deters crime also exists with the Rangemaster trainee's incident database via Tom Givens and Claude Werner's surveys of reported shootings.
I suspect that some of the problem among the population about accepting conclusions on CCW relate to whether a person views themselves as having agency (the ability to act to change circumstances)--or whether they view themselves as unable to act. Guns in society have largely been portrayed in media as evil things that result in death of other humans or animals instead of a tool. Gun use in suicides, crime, and hunting, leave those who do not believe they have any influence on these things desiring restrictions via laws and policies. If you think of these as akin to sympathetic magic--you would be correct. Thus, a gun-free sticker on a building magically transforms it into a safe place without violence and a state free from guns would be free from violence because the "gun" is the cause, not the individual criminal. Those without agency look then for narratives that confirm their prognosis that guns provide the means to kill people and are ineffective in preserving an individual person's life or liberty through self-action. Thus, "government". "society", "police", or "laws", which are all abstract institutions are viewed by those believing themselves powerless as the only effective ways to combat violence. Some, not all, are willing to excuse criminals for their acts because of similar abstractions that "force" the criminal, terrorist, or the criminally insane, to act as they do. Any evidence to the contrary simply will not be accepted--even a story where an armed citizen stops a crime will often be dismissed as two wrongs don't make a right and that that citizen's actions would not be necessary if guns were banned.
Obviously, those who believe themselves to have agency believe that an individual's actions matter and can change things. I suspect that these people are more highly correlated with those possessing ccw and firearms. If one looks at a gun unemotionally, it is a tool and the real threat is the individual who would use it for evil rather than the tool itself. Thus, a bad guy with a gun can be countered by a good guy with a gun. If I substituted a car for a gun, once again it is a tool--it can be used as a getaway car for bad guys as well as the police chasing them. The real threat is the person behind the wheel behaving evilly rather than the car itself (aside from Stephen King's Christine). A person with agency doesn't believe that accidents are inevitable--instead they would analyze and process information about other drivers and then act accordingly. If someone ahead is driving like they are drunk or deranged, you call the cops and slow down etc. Thus, a person with agency uses information as a tool to determine the best way to act rather than simply ignoring reality as it is.
