here's a hint. when writing a response in my situation - start with writing two ...
the first is shorter, simpker, and how you really feel.
the second is longer, diplomatic, and what the organization wants / needs from your perspective. the first one gets the emotion out of the way. and you can refer to it for perspective - the one you don't want officially expressed.
this is how i started ...
On Wednesday April 22 at around 5pm I was involved in an exchange with clerk 7777, xxxxx
XXXXX is a cunt.
i left that at the top, until the real response was done.
made it much easier to deal with.