The problem is that it is easy (far too easy) to see 'short and to the point' as being rude.
And who really cares when you got caught in the shop, red-handed, filling your pockets.
So far we have had over half the discussion about whether the inspector was "rude" based on the sole testimony of the OP, who:
- repeatedly misused the contactless function by deliberately not tapping in and out properly
- did, in fact, evade fares, and likely would have continued to do so unless caught
- was caught, red handed, tapping only their flexi ticket at Marylebone which was not valid there, or anywhere near there
The only advice we can give the OP is that there is ample evidence not just of failing to show a valid ticket but also of attempting to evade the fare, so it is better at this stage to focus on:
1) Attempting to settle the matter out of court, and if unsuccessful,
2) Mitigating their actions by trying to argue there was no intent, leaving only a bylaw prosecution feasible.
Unfortunately though, Chiltern do appear minded to take people through the courts to deter exactly the sort of misuse and fare loss that has happened in this case. The OP has about as useful a defence as a man caught with a nice joint of beef up his jumper going out the door at Tesco but claiming he "just wanted to test the barrier there, I'll sort it all out later!". Then on brief investigation he's done it twice this week already and according to him it's all straightened out, but there's already ten quid short.
It looks bad, and we should concentrate on that rather than whether the person who detected this was "rude".