The problem with guns as defensive weapons is that aggressors using guns always have the massive advantage of surprise. And that defenders may make mistakes.
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So at 3am you are awakened by sounds of movement in your home. You grab your 9mm and prepare for combat. You see a dark figure.
Pow pow pow.
Oh dear, it's your son who let himself in not wanting to wake anyone up.
Correction -— it was your son.
Reminds me of that South African Olympian athlete now in pokey who thought it was an intruder but shot his girlfriend. Or maybe he was just pissed at his girlfriend.
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So at 3am you are awakened by a presence in your room. No time to get the 9mm out of your bedside table.
Pow pow pow.
It's your daughter firing — at you; pissed that you won't let her go out with unsuitable persons. Or maybe it's your spouse, pissed that you are such a horrible person. Or maybe it's a hitperson hired by your spouse, who wants your loot so he/she can go marry someone she/he really loves. You see the problem with weapons is that it is not a one way street. You can use them. But others can use them against you.
Or maybe you stupidly forgot to put the 9mm back in the gun safe and your 2 year old finds it and shoots -- could be you he/she shoots -- or heaven forbid, herhimself. Or, hopefully, just a hole in the wall. But wait... what the hell use is a 9mm locked in a gunsafe ? To be any use at all for self defense, a weapon has to be on your person at all times you might be exposed to a threat. Which if you want to be truly prepared, is any time of day or night.
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Okay, so you are prepared at all times. If you're a guy you have a shoulder holster and are wearing a coat at all times to conceal your weapon. Ditto if you're a gal.
You are driving home at 9pm. But wait, your regular route is blocked by an accident. You are diverted through a bad part of town... all kinds of baaad things can happen. Like someone thinks you are a driveby shooter. Pow pow pow.
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You see the offense usually has a distinct advantage. Unless they are attacking a vigilant opponent who sees them first.
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What about being in a crowded cinema. A gunman enters from behind and starts firing. Three other people with weapons start firing. They fire wherever they see muzzle flashes. Pow pow pow. Bam bam bam. Oh dear... half the audience has guns... 32 dead.
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Sure, you can construct scenarios where you are Lone Ranger, and are a total hero who saves everyone through expert use of your 9mm. Very rousing to the adrenaline. But it's quite possible you may commit involuntary manslaughter because you miss the bad guy and... collateral damage.
Like you are in a convenience store at 7pm and two gunmen burst in firing their weapons. Everyone ducks. You break cover for a moment with your trusty 357 magnum… pow pow pow… too slow… you’re dead.
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So, all in all, there are so many ways guns can go wrong.
They are made to kill. And maybe one might kill you. So lowering the number of people with guns... is going to reduce the likelihood someone will kill you.