Sorry Len, that was too good to pass up! Lol
I mention that only because it is possible that the entire scene might be related to the older guy's intolerance of "different lifestyles". I didn't see/hear what started the fracas so can only offer what I did see/hear that might explain what happened. The fact that the argument was supposedly about "manspreading" to prevent him sitting down, yet a young lady was able to sit between the combatants just doesn't compute in my mind.
The last time I rode the red line was about a year ago, I observed an MBTA worker that was just getting off of work board the train. She eyed the seats carefully, found some discarded newspapers and put them on top of the seat she intended to sit in. She paused for several seconds then sat down on the newspapers.
She saw us looking at her and felt compelled to explain: The plastic seats with dark carpet upholstery hide stains she said...and hold wetness too. More than once she's sat in a puddle of questionable liquids, including urine, at the end of her shift and this was her method to limit the occurrence of that unpleasantness.
I hate public transportation, and I prefer to stand.
I'm not fond of the subway lines, but it sure as hell beats driving in circles to find parking in the city, paying $20-40 for the "privilege" and still having to walk a mile from your parked car. The commuter rail is usually just that, very few vagabonds and mostly professionals who work in the city but live in the 'burbs.