Another issue raised is that were there no revenue protection present at LMS anybody in the same situation would not have had to buy a ticket.
This seems to me to be the basis of the argument, and is wrong. Of course they would have had to buy a ticket. Buying a ticket (before travel where possible) is not something you only do because the nasty man on the train comes around or because you get stuck behind some horrid barriers. It is the law.
You also keep referring to a £20 "slap on the wrist". Penalties for non-payment are meant to be a deterrent, not a "slap on the wrist".