Earlier quoted context omitted.
I've found that looking the person in the eye and giving a quick "hey, forget your headphones?" sometimes does the trick, and has yet to start a fight. Everyone has to act in ways they are comfortable with - but mass inaction is what creates space for this shitty behavior in the first place.
I did this on a bus and had a gun pulled on me, so your mileage may vary
If you ask such person to stop it is implied they expect you to back that up with violence and you've already consented to a battle.