The writer of this letter was not very bright, imo. Their intent was to cast aspersions on the SA's office and the evidence gathered to charge KC. This attempt is not all that interesting to me, personally, for all the reasons posters have mentioned.
However, what will be extremely interesting to me will be the release of the SA's evidence which will be the only response needed to this pitiful letter. We may have to wait until trial to see and hear it - but, that's okay. It will be accurate and not a mish-mash of stuff. You won't have to read and re-read the state's evidence. It will be concise and compelling.
My humble opinion, of course.