When cultish beliefs substitute for sane perception of reality and processing reality in logic and reason it makes no sense in attempting to dissuade those so entrapped. For cultists, the holding of belief is more important than reality, reason, sanity, empathy, compassion and even life - usually the life of those who question.  These values confuse the cultist, cause anxiety and the impulse to fight (rejection, vitriol or violence) or flight (hide behind a wall- literally or figuratively). The "absoluteness" of the belief can be attributed to deity, "legitimate teaching authority",  emperor, cleric, but it is either a cop-out from their humanity or exploitation of a susceptibility.
What is important is that people with reasonable capacities for discernment ask why aloud. Ask "why" of the belief. Ask "why" of the believer. Ask "why" of the perpetrator whose self interest is involved. You will not find "truth" from the cultist. You can only hope and pray.