At a sufficient enough and above. Below that the Clerks (as in the Kevin Smith movie) treatment is good enough.
In any case, "treating like a real human being" and putting on a show of smiles and friendliness US-style, is not even close to being the same thing.
In "real" human interaction, we understand the other as a person with their own feelings and mood, and we don't demand from anybody to exhibit a certain cheerful mood for us.
But of course this isn't about real human connection. It's more about "When I pay I demand those serving me to entertain me with smiles and pleasantries". The customer could not care less about the person serving them, or their condition, otherwise. "Real person" my ass.
Not all of us have had the luxury to spend our lives musing about trivial things like RuneScape, in between posting on white-collar tech forums.
I don't think you should read so much into my hobby either.
I’m also skeptical of the extent of your actual experience if you think this behavior is “out of line” in American society. It was quite routine in mine. The first time I saw someone throw food at the head of a cashier I was shocked, but quite quickly became inured.
You tried to attached the American cultural norm of manners and courtesy to their history of black slavery.
"Get a grip" is a pretty mild response to something so absurd, hyperbolic, and flat out insulting.
E.g. Not getting enough sleep because your poor neighborhood is a ruckus provokes bad mood, chronically.
You are asking the poor to have sympathy while not showing them empathy
Why does one's income level dictate how they treat others? I was always told treat others how you would like to be treated.