There is no true believer stronger than the converted
The staunchest conservative is a liberal who has been mugged.
A lot of the answers you are looking for are simple. People have a tendency to go "overboard" when they feel strongly about something. Religion, politics, morality, self defense, sports, pick any subject at all, and you will find a percentage of the enthusiasts who take it as far as they can. Sometimes they know what they are doing. Other times, they don't.
A lot of the time, people will choose the latest whiz bang tactical hi cap weapon, because they get told it is the best. Or they may choose what the police carry. Or yes, what they see on the screen, in movies or video games. These people are almost always neophytes when it comes to guns, shooting, and the moral and legal issues surrounding self defense.
Yes, they believe that the gun will protect them, assuming automatically that they will have the skill and opportunity to use it correctly. And the "badder" the gun, the better job it will do. And our entertainment industry constantly re-enforces this unrealistic expectation. People who know guns and shooting seldom have this belief. We know guns are not magic wands, and there are no magic bullets, that never miss, and always stop attackers with a single hit. It just ain't so in the real world.
As to our world being more violent and dangerous than it used to be, I havesome ideas, but I'll save them for another post, if the thread stays open.