Something interesting happened at lunchtime

I went to pick up some chinese take out and started parking. As I was halfway into the spot the car on my left suddenly backs out (diaganally no less, straight in my direction). Naturally I honk, no biggie. Stops and I park in. This is where it gets interesting. I noticed the car didn't just leave, it just sat there. So looking at the driver, he stares at me in a semi-stoic posture, his passenger was more relaxed. Naturally, I figure he must have something to say or waiting for my acknowledgment (although I was wondering why, since he was clearly didn't look behind him as he was backing out).

So curiously I pointed out casually,
ME: "So you didn't see me coming in huh?"
DRIVER: (I think he was working himself up or something)
"So you didn't see me backing up?"
ME: "um, my car was already half way in the spot before you started backing up?" (pause) "you didn't even look huh?"
DRIVER: (flicks me a middle finger)
ME: "Nice attitude"
DRIVER: "What don't like it?"
ME: ( I turn around and dismiss him)

No need to say what that guy was, but what I don't understand is how American society is anymore. It seems the first reaction of people is to blame others or exhonorate ourselves from fault or responsibility and not only that, act instinctively the opposite. As if we have stopped to think rationally and put aside whatever is sensible or logical. Instead we replace that with our justifications.
I admit, I have been unreasonable a few times in the past, and I think I fall under the same problem. What is it that causes this angst? Is it the pressure from work? Pressure from our lives? Whatever the cause, a bad day, bad mood, a problem, doesn't give us the right to go around being an asshole. Some people are ridiculously wealthy being just such and have succeeded in life, but the ends certainly doesn't justify the means or so the saying goes.

This antedates to the BUS UNCLE video clip. Different situation, same style of idiocy, although BUS UNCLE was abusive to the point, you have to fight.