> For example by the time someone is answering their front door with a gun and pointing it at whomever is there, it's clear that person is suffering from a paranoia that should make them ineligible to possess firearms.
First, let me say that "pointing at whomever is there" is a big step too far. Also, arbitrarily pointing a gun at someone who is not a threat to you in order to intimidate them is already a separate crime in the US - "brandishing". In the few states that don't have specific brandishing laws, that act typically falls under "assault" or "assault with a deadly weapon".
That said, it's very common for people to answer the door armed. I do. Generally that's a holstered pistol on my belt, but if I'm not wearing "street clothes" at the time it could be a tiny pistol in my pocket, a full-size pistol in my hand behind the door so it can't be seen, or a carbine similarly concealed.
Why? I grew up in a place where police response averaged a half hour or more. My home was a half mile (~0.8km for those of you outside the US) down a private gravel road; if someone was at my door that I didn't expect or recognize, chances are they were unwelcome. Generally that means salesmen, but we weren't the only people familiar with police response times, so precautions were well-founded.
Today it's partly a habit for me. Like many people, I have a cloud-connected camera system around my home and a doorbell camera. I never have to go to my door without knowing who to expect when I open it. It's not entirely habit though - if I'm physically answering the door and don't recognize the person on the other side, I can reasonably expect that the purpose of the interaction will be to eject them from my property. A firearm is nothing more than a tool to facilitate doing that with minimal risk to myself and my family.
> And this should be policed by other gun owners!
We do! Gun stores have the ability to deny a sale to anyone, at any time, for any reason. They exercise it regularly. If you don't believe me, find someone who can legally own a firearm and have them go into a gun store while smelling of weed, or alcohol. Alternatively, have them act erratically in the store. Then ask to buy a gun. Chances are they'll be refused service and told to leave at that point. If not, the person at the counter will give them a "Form 4473". There's a fair chance that the employee will use the time spent by the customer to fill out the 4473 to call the police. If the customer fills it out and their answers indicate that they are not a prohibited person, expect the employee to call in the background check and then pretend that the response is delayed. The customer will be instructed to come back later, at a specific time or when called. Police will be present when they're told to return.
Seriously. I've worked in a gun store and spend a fair amount of time in them, and I've seen this (or variants thereof) play out many times. If you come in and can't suppress your crazy long enough to hold a courteous conversation, you're not buying a firearm from them.
> But it's been drawn into this culture war where if we admit that Crazy Bob perhaps shouldn't have guns, then the "liberals" win or whatever.
What I see is that we're not afraid to "self-police", but see attempts to pass laws with an arbitrary means of depriving citizens of their rights without due process as a (rather obvious) attempt for the government to acquire the tools to disarm citizens at their leisure. In other words: it's not that we think Crazy Bob should be armed, but that we would much rather risk Armed Crazy Bob than to give the government the ability to apply the "Crazy" monicker to whomever they like.