Social Etiquette: Standing in the Train doorway

Today while standing on the train I discovered a great way to piss people off but it wasn't through my own actions. Rather it was a simple matter of watching a middle-aged man in a pin-stripe suit irritate the people trying to get into the train. The train carriage was not completely full and on stepping into the train he decided that his little "place" on the train would be that section just inside where the doors shut. He had a choice of almost anywhere else in that section of the train, but he chose that particular spot. The problem was that his decision was premature as there were still people getting on the train. I was his mirror self. I stood directly opposite, in a very similar position in the carriage to where he was standing, however with a great difference. I was not where the doors were still open. So the first person after him was a little asian lady. She had to physically push him out of the way with both her hands while saying excuse me and with an exasperated look on her face. He barely moved and was either clueless or rude. The second person, a larger guy, was a fair bit bigger and of a similar build to the door-blocking man and as the doors were preparing to close he threw himself into the train and knocked the guy to the side. He said, "What the hell are you doing? Get out of the way of the door. Jeez. People are trying to get on and you are just standing there in the door. What are you an idiot?" To which the vague man replied, "I was standing there". The angry man continued to yell at the guy and the guy continued to claim that he was simply standing there and neither ever got to a point where they understood the other person. So, as a lesson in social etiquette for everyone: it is polite to not stand in the doorway of trains while people are still boarding and for that matter any doorway while people need to walk through it.