Weird Fat People On The Subway experience. What to do?

This story is adapted from me telling it via GChat, so forgive the style. So today I was on the NYC subway, and there was this fat lady who was sitting next to another fat lady and then there was a .75 person space and then another dude. There was the bar divider between the two fat ladies, So it appeared to be: [ ]_( A ) |( B )[ ] [ ] [ ] = person ( ) fat lady |= Divider _ = space So i came in and, not having a big ass and hoping fat lady A would move, attempted to sit in the space. However, fat lady A was not moving over so i just stood up and walked to the pole, and stood, annoyed but whatever. Then, another dude attempted to do the same. He got up, after trying, without saying anything. And then another dude in a suit attempted to do the same, he looks around annoyed, we make eye contact, and shrug and I say "dude, you're the third one to try." I look away, look back and, I see him arguing with Fat lady A. I had my headphones on so i don't know what he said, but she got up and stormed out at the next stop Then, he lookeds up at me and said "do you want the seat" and i took it becuase what was i supposed to say, no? so now it was [ ][ ][X]|( B )[ ][ ] and I'm X and i notice that fat lady B is actually pushing onto my side, meaning that the fat lady previously sitting there couldn't have possibly moved because the actual (original) situation was as such: [ ]_( A )(| B )[ ][ ] However, B faced no embarrassment/argument, despite her being the real problem. And i felt like a jerk for benefiting from the jerkiness from the dude sitting next to me. What would you have done in the situation?