Just read that letter. Either there was some sort of misunderstanding or the controller/radio operator was completely out of order. Either way I don't imagine the matter will end there. I seem to remember reading a report recently (CHIRP?) about controllers/operators getting shirty when the wrong callsign is used i.e. calling them 'radio' when they should be 'tower' etc.; I don't think the CAA take a very positive view of that sort of pettiness.
AMEandPPL, I would say that if true that is an MOR matter, not CHIRP; nothing confidential about it and far too serious.