The challenge to Muslims is to ask themselves some questions, and examine their own thinking:
Once indoctrination has taken root within an individual, any attempt to expose fallacies, 'rock the boat' or even what might start out as a purely rational discussion with that individual about alternative points of view, will typically evoke anger; a subconscious attempt to turn it into an argument and to 'win' that argument - at least to their own satisfaction (not anyone else's).This appears to be driven by a regression on the part of the indoctrinee to their parental and child modes (as per Transactional Analysis). The original adult rational conversational prompt, causes conflict and confusion which must be overcome somehow. Without any rational way to respond, the parental indoctrination kicks in, along with anger from the child mode.
Try reading testimony of people who've left islam. You may read the first few and try to justify yourself... They were never 'true' muslims ... They were unlucky ... They were had inadequate teaching ... They drew the wrong conclusions... But doubtless you will eventually see something of yourself and your own situation there.
Just as an aside; UK coinage includes the Latin abbreviation "Fid. Def." (Fidei Defensor) because the monarch is the head of the Church of England and defender of the faith. See this link for more details regarding British coinage.