utter indifference Dictionary.com on indifference:
lack of interest or concern: We were shocked by their indifference toward poverty.
unimportance; little or no concern: Whether or not to attend the party is a matter of indifference to him.
utter, as an adjective is explained in Collins English Dictionary:
You use utter to emphasize that something is great in extent, degree,
or amount. [emphasis] This, of course, is utter nonsense.
...this utter lack of responsibility
Example (made up):
I am utterly indifferent to your opinion on this or any subject.
Please allow me to get back to work.
Translation: Shut the f--- up and get the f--- out.
The OP's example becomes:
X is utterly indifferent to ...... or X's utter indifference on the subject of ..... is "indecent" or "astonishes me" or "is incomprehensible" or "flies in the face of reason"....I am sure the reader can supply appropriate words of incredulity.