May I add my own ad nauseum? People believe they can tell who a criminal is, but they really can't. In movies we all know who the baddie is because he is ugly, acts creepy, the music gets ominous and the camera angles change.
IRL, the baddies look and act pretty much like everyone else, right up until they do the crime. There is really no way to tell that someone is a potential
criminal, because they are not a criminal until they do the crime!
I have had this argument with pro-gun people after a public shooting. They insist that having more people armed will be a good defense against the random crazies who shoot up schools and malls. But when you break it down, there is no way that can work.
Consider: You hear shots and run into the school hall or middle of the shopping mall with your gun out. You see a guy with a gun. Do you shoot him? How do you know he is not another hero wannabe, just like you, who came running out looking for the bad guy-- who has already fled the scene? How do you know he is not a plain clothes cop also looking for the bad guy? How do you know if the shooter is not a guy at all but a woman? How do you know if there are several shooters, not just one?
Answer--you don't know
Having a gun may make you feel safer, but that is an illusion. It may make you do stupid things you would never do if you did not have a gun, like confront armed crazies.
Witnesses sometimes identify the wrong person. The police and security guards mistakenly target innocent people who looked or acted "in a suspicious manner". Adding more guns to an already chaotic scenario guarantees more innocent people will be shot.
The only real way to be more secure is to do the touchy-feely liberal things that more peaceful countries have, and that conservatives hate: give people with mental or drug problems access to counselors; have programs for disaffected youth; give veterans good services; give folks who get fired or lose their jobs some income and health care; in other words, have a social safety net to catch people who might otherwise "go postal" with a gun or try to commit "suicide by cop".
And, as long as we in the US plan on letting pretty much any untrained person have as many guns as they can buy, maybe we should keep an eye on people who seem to be getting antisocial and are stocking up on weapons.