'I'm not the agent': Customer at apartment viewing gets confused by another interested renter as the agent, he clarifies he isn't, but they don't believe him and keep asking him questions about the apartment

Entering an apartment viewing, assuming the person there is an agent, get told he isn't, don't believe him, and then the agent actually entering the apartment seems like a problem of entitlement, or maybe you can't understand what other people say… 

It baffles me that all the stories about people getting mistaken for employees, them telling the customers that they are, in fact, not employees, and getting ignored and asked about something in the store. You cannot tell me that the attitude is not expected in a mean way. You can, of course, confuse someone for an employee, but if you're told that they aren't staff, you say sorry and move on. Don't you? That's what I have done every time something like that happens. I wouldn't even dare to question someone's word in general. But especially not when they're telling me they don't work there. If they did, they wouldn't lie about it. Is far more common for someone to lie saying they work there than the opposite, so why not believe them when they say they are just a customer like you and me? 

Let's picture for one moment that I go inside a store. I see a person with a red shirt, like the one that the staff uses, so I assume that they are an employee. I go up to them and ask if they work there; they say no. Now, for the sake of this hypothesis, let's pretend that I don't believe them; what would I do? Confront them? Tell them they need to find their manager? Call out to corporate and complain? The whole situation is completely bananas. Isn't it better to just go around looking for someone else? Isn't the most sane thing to do just to believe them? Don't these people realize that they sound crazy when doing all that? Let's pretend that in this hypothetical situation, the employee lied; they did work there, and they are now in big trouble even if I don't complain, because this will eventually be known by managers. So what is the benefit they receive by lying? Nothing. So why would they even do it? Spoiler alert: they don't. 

To sum it up, if for whatever reason you get into a situation like this one some day, please do not act like this. It is the behavior of a crazy person, and it brings literally no benefit to them or you. When you doubt whether someone is telling the truth or not, you just need to think of something very simple: what's in it for them if they are lying. If you can't think of a single reasonable reason for them to be doing that, the there a 99% chance they are telling the truth. This advice may be useful for more situations like just this one, so keep it in mind, and, please, think before you act. I promise you it's not that hard. I can't believe some people need to be told that to begin with.