It's not about what your interpretation of what is ethical might be. It's about you following the rules as they are laid out to protect yourself against being penalised. I find it hard to believe that people will part with their money, not having the first clue as to what they're actually buying. I suppose you'll call me unreasonable because I check what I'm letting myself in for prior to parting with my money.
I thought I was sufficiently clear before, but I'll really try hard this time and try again for you.
I'm not questioning the terms of the contract, the terms of the Conditions of Carriage, or whether a Penalty Fare is valid. Sure people are agreeing to terms and conditions, they should read them. Good for you, some people like rules and regulations, it gives their life structure and removes all doubt or risk or the unknown.
What I was saying, is that the just because a rule is there - and I'm not trying to say for a minute that it should be deemed invalid, or that a PF appeal should succeed - doesn't mean it's ethically right.
Lets try a particularly pedantic example. e.g. a ticket remains the property of National Rail etc and can be withdrawn at any time. Lets say you get on the train, RPI withdraws the ticket, then PFs you for not having a valid ticket. NR CoC says that's fine (at least ambiguously). Sure, for the people that are only able to comprehend rules, that's just great. Passenger should have read the NR CoC and.... decided against travelling by rail, more fool them.
My point is people expect rules to be sensible, understandable, and in some way predictible. I'm not saying that the rules as they are are in some way unenforceable. But in this example, they are not what any sane, normal human being would expect. Which is fine, but it should be advertised better and people made aware of it.
Imagine going into a McDonalds, and on the back of the receipt that you throw away instinctively, it says 'See T&Cs'. Mr Puberty on the till doesn't know what Tees and Sees are, suggests you see the website. You eat half your cheeseburger and chuck the rest away. You get a £20 Penalty MealDeal because you didn't complete your burger (to cover refuse charges, of course), but that's ok, it said so in the T&Cs, which you should have read! Sounds ridiculous!
When the concept of travelling less distance, yet paying a fine for doing so, is 'perfectly understandable, you should have read the T&Cs, the above example doesn't sound so ridiculous!