For the same reason I don't think that TTC drivers should be obliged to enforce fares, I also don't think that regular riders are under any obligation to police asocial behaviour. The people who engage in said behaviour are frequently violent and/or strung out on drugs, and the average person is not trained in any way to respond to such a situation.
Up to a point, I'm sympathetic w/this argument, but I do think it needs to be situational.
If we're going to insist that no one can ever call out anti-social behavior unless they are either 'John Wick' or willing to press the alarm and potentially hold up an entire train of people for 20 minutes, then too much ill behavior will proliferate.
Taking a pass on saying something for a minor transgression of etiquette is fair; and so is avoiding a direct confrontation with someone who appears unstable or dangerous.
But there is a space between there, and letting everything go.
I let a lot of people go when are openly (no earbuds) playing music on their phone, even though I consider that irksome, and rude, because I weigh the costs of intervention vs the nuisance value of non-intervention.
On the other hand, I've told people to get their feet off the seats more than once.........
And last year, there was someone who was definitely unstable getting up in the face of a female passenger and clearly scaring her. I stood up, inserted myself between them and backed him up off the train. I'm not a hero, it was a move that carried risk, it was also the right thing to do, and I'm not particularly young, nor a martial artist.
But passivity to excess is as corrosive to society as constantly inserting yourself into the business of others.