Let's face it, a minimally astute bureaucrat would have at least agreed to acknowledge victims' letters.  They would have gained a modicum of credit by showing a minimum of respect. AND, in addition, they/Muller would have a) been consistent with the supposed "subsidiarity" - which he stupidly gave as reason for refusing thus contradicting himself - AND, b) would have "covered their whatever" by offloading further responsibility for to the local Bishop, as per P. Pilate, "washing their hands of the matter". 
Everything else Muller wrote - especially the fact that he put it in writing - seems to be a personal effort to dig himself and his cronies deeper into the very hole that they dug for themselves. 
This wee comment on "bureaucratic" incompetency - is merely an addendum to the incredibly more important comments on the lack of ecclesial integrity revealed by Ms. Collins and comments below.
Point: add incompetence to systematic and systemic abuse. 
Jesus has left the building.