>A single disapproving grandmother can put a stop to it.

I think you have to go further upstream socially - there are people that should not be free, but are. Public transit has not just loud talking or music on phones, but the mentally deranged, babbling, even actively drug using population walking a knife's edge between erratic and aggressive behavior. From my POV it's so far past a stern stare on the US west coast that the suggestion comes across comical.