Something I have several times encountered when visiting the US is quite angry responses when I innocently step out of line using a bus, or buying something in a shop. Quite a high fraction of these incidents result from interaction with people from disadvantaged minorities.
The University of Michigan has an amazing free bus system to work around its highly dispersed campuses. Even in off-peak times like the summer break, you seldom have to wait more than 5 minutes for a bus. This morning, I climbed onto a bus rather quickly, in the interests of allowing the driver to move off, and didn't see someone planning on getting off, who had been standing a little back of the door.
The driver really chewed me out. I had seen that guy standing there, and showed no respect, walking right in his face.
If I had really done this, he would have a case, but how did he know what I had or had not seen? It would have served his purpose just as well if he had made the same comment in a lighter way -- you didn't really mean to do that did you? You should look where you are going. I would have taken the point without feeling someone was trying to be obnoxious to me.
A few days back, I was shopping in the Borders bookstore (I believe the Ann Arbor branch is the original). No one was waiting to pay, and it wasn't clear where to line up, so I just walked up to the nearest till. The cashier, who hadn't been watching me before, got very annoyed, and gave me the same kind of "who do you think you are" response. Who I think I am is a stranger in town who doesn't always see things which may be obvious to locals.
Some years back, when I was visiting Palo Alto, I had a more extreme case of this, after I arrived at San Francisco airport. I knew I needed the 7F bus between San Francisco and Palo Alto, in the Palo Alto direction. A 7F bus arrived, and as it stopped, the scrolling writing on the side wasn't showing the direction, so I climbed on and asked the driver if he was going to Palo Alto. He grunted something which sounded like "Yes". In any case, I knew that the bus service had a rule that you weren't allowed luggage if you were doing the segment between the airport and the city. What's more, I paid him the fare for Palo Alto, not for the trip to the city. Soon after we left, I realised we were going the wrong way and asked the driver about it. He was uninterested in my problems, and I had to go into the city and wait a considerable time for a bus going the other way. As I climbed onto this bus, the driver started yelling at me for bringing luggage onto the bus. I eventually managed to get the words "Palo Alto" out, and he said, "Why didn't you say so?" like it was my fault he was rude. I wrote a letter to SamTrans complaining about all this. It's not that the bus fare was very high -- only a dollar or 2 -- but I would have expected at least a form letter back, but I heard nothing from them.
No doubt those drivers are still there being unpleasant to random strangers, which is a pity, because their jobs depend on the service they are offering. Not only their jobs, but those of the other drivers who are nice and helpful.
Don't get me wrong. I know some people have a good case for feeling hard done by. The US in the 21st century is still a very unequal society. But picking on confused strangers doesn't solve the problem. All it does is increase the hard-done-by person's own feeling of bitterness. When I go home, these unhappy people will still be unhappy.