Regardless, no punishment is too harsh, this should be considered the equivalent of lighting up a cigarette on a plane.
On topic (and discussed already on HN): https://github.com/Pankajtanwarbanna/stfu
There are a couple of us who have actually seen someone call them out that are warning folks here what commonly happens. I saw someone get attacked with a knife, another commenter here had a gun pulled on him when they asked them to stop. It isn't about the loud music itself, it's that they're openly saying they are king shit, that no one is willing to challenge them, and broadcasting their eagerness to deliver violence upon anyone that might.
The other side of this is that they often do it on places you can't easily escape, like a train car with stops only every 5 minutes. This gives them a very long time to go to town on anyone that might challenges them. Something I've seen with my own eyes when they were asked to tone down the music.
There are angry people playing dominance games on one hand, and on the other people who simply don't care what anybody else wants and will do what they can get away with. There's no difference in intelligence between the two, but only the first type can actually be reasoned with. The second type will only pretend to be reasonable until the person that they're intimidated by leaves the room.
Everybody says "social cues," but as you said, the people who "don't get social cues" also don't seem to "get" direct requests or orders.
Okay this is ridiculous. One is a fire hazard and the other is not. Do you really need the hyperbole here?