What's the big deal?
This happens all the time on British trains - I must have seen it dozens of times, particularly when people guess the guard won't be round before their station comes along.
As long as the people pay up or move out when challenged, don't try to rub my nose in the fact they haven't paid, I personally don't have a big problem.
I get really p@@sed off with the snobby class attitude that still pervades in parts of the travel world. A few weeks back, I was fortunate enough to blag a couple of free first class return train tickets. My partner who doesn't normally travel long distances by train, and first class at that, was was quite excited, and she was chatting to the couple opposite about our free tickets, when a couple across the aisle were heard to say "I think people on free tickets should be in a different cabin to paying first class passengers". We were both careful to ensure we passed our scabies, plague and lice onto these full fare First Class snobs before we left.