If your first argument is that many traffic violations are not victimless crimes, then the solution should be more, not less law enforcement, consistent with holding fare evaders accountable.Feel free to call the police every time you suspect someone is fare evading. However, make sure to also do so for every other transportation crime that's committed. Someone going 1mph over the speed limit? Call the police! Rolling through a stop sign? Call the police! Expired registration? Call the police! As for victimless crimes, the first two especially are not victimless crimes - tens of thousands of people die on the roads annually in the US, and some of those are through inattentive driving or speeding.
I'm going to guess that within a couple of days of diligently reporting every crime you see you'll get, at minimum, a very stern warning by the 911 dispatchers to stop calling them for such things.
And if the passenger refuses to pay the fare? It's going to be impossible to know how long the train is delayed if the passenger is non-cooperative, if a more important emergency comes up for the police en route, etc.
For your second argument: my position is that Amtrak should have a fare evasion policy that minimizes costs on Amtrak. Some discretion would of course need to be left to Amtrak staff at the time someone is caught. For example, if someone just jumps onto a full, late Acela and is immediately caught, the penalty and process wouldn’t be as severe as someone who’s caught stealing a ride worth $750 on an empty train.
What I dislike is letting fare evaders ride and then be done with their trips, with no consequences. If someone is a regular commuter between Philadelphia and Metropark, NYC and Newark or Newark and Metropark, why not ride the Acela for free, without consequences, when the alternative is NJ Transit.