Look, you can look through my post history if you don't believe me, I'm no simp for cops or authoritarians, but this is kind of a bullshitty line of reasoning. Maybe it's because I was raised around guns and was taught gun safety, or I have a friend who was a deputy (he quit under Trump for ethical and moral reasons), but what you're proposing isn't all that simple. It's like asking someone to discern if a dollar bill is a counterfeit by showing it to them from out of arm's reach for five seconds without warning them first; sure, some dollar bills, like the one my kid made, will very clearly be fake, but even a half decent fake would pass the sniff test under those conditions. For some folks, a subset of monopoly money might pass under those conditions. There's a much greater personal risk involved in assuming a gun is fake than assuming it's real; after all, enough people have been shot by "fake", "unloaded" guns purely by accident.

A personal story: I'm a paramedic. Once we got called to someone having altered mental status. When we get there, it's an older guy who's clearly acutely confused; he came out to the ambulance, pointed at a component on our door, and asked if it was a camera (it very clearly was not) and then went inside without waiting for an answer. He was agitated, talking nonsensically, confused, and not following commands. As I'm trying to calm him down enough to get him to come with us, he wanders into the kitchen, and I follow. He stands next to what is very clearly the grip of a pistol sticking out from under some paper; only the barrel and slide are hidden. I wedged myself in between him and the pistol and blocked his access to it. My partner later came back to check and found it was an airsoft pistol. Mind you, I've played airsoft, I've used airsoft pistols, but for all I could tell in the moment, it was a real gun. Now, do you think it would have been smarter for me to stop and closely examine the pistol first? Doesn't it make more sense to assume the more dangerous possibility until it's ruled out?

You do have a point. What would happen if someone with a real gun shot up a school, and during the investigation it showed the killer interacting with a security guard at the front of the building, who would later say, “they said it was fake so I let them through”