All related to that post.
So basically the OP is being criticised for telling the truth. The person who originally considered the case didn't have the necessary literacy or cognitive skills to correctly assess the situation and it was only when a manager, got involved that the situation was correctly resolved. A manager supporting their staff is great. A manager doing so when those staff are palpably in the wrong isn't so great. Said manager having the chutzpah, when he has zero right, to tell a customer to watch his tone would, if l was the OP, be the subject of a formal complaint about his own attitude and tone. God forbid that a passenger/customer might want his case dealt with quickly and accurately and be less than ecstatic if that is not done.
I actually agree that people should be treated politely and with respect; that works two ways though. Why do the railways believe that they can treat passengers like utter crap and yet demand that staff are always dealt with politely?
A policy of flagging what are perceived as "problem customers" is perfectly fine - just as long as your company never makes any mistakes (oh, and could be bloody embarrassing if a GPDR SAR ever comes in). If it does then the policy is only likely to lead to more complaints (in the bank example cited to the Ombudsman) and/or litigation against the company. That has serious costs. Customers can make it hurt too.
Trying to argue that a letter to a TOC complaining about how a case was incorrectly handled by railway office staff constitutes bullying or harrassment is covered by railway byelaws is a new low in the demands for the railway to be treated differently as something special. If it was the OP l'd say "take me to Court then' to the TOC and would ensure maximum media coverage and questions from my MP to Grant Shapps. Most people hold the railway with precious little respect as it is and that would only be amplified. Hopefully the outcome would be a major rewrite of the byelaws to remove the current egregious imbalances.
Were l the OP l would be writing to the TOC CE demanding an apology for the attitude and tone of the manager's response letter. As an upper mid level civil servant of over 30 years standing l know that any colleague in a public facing role who presumed, in response to a factually correct complaint, to lecture a member of the public for their tone would rightly be subject to disciplinary action.