The delicious irony is that he’s getting jacked up for calling himself what they call him. Sort of the converse of “we can call ourselves niggers, but don’t you care call us that, honky”. And no, I didn’t asterisk the letters, because it’s not a curse word. It’s ugly and objectionable, but it’s not a curse word.
It’s strange they’d be offended by the man tagging himself as an infidel.
Also kind of strange that a person in their right mind would tag themselves with it.