This isn't right. If I believe wholeheartedly that fire can't hurt me and constantly try to walk into burning buildings as a result, you calmly trying to convince me that I'll be hurt by doing so isn't fanaticism. You're looking out for my well-being.
By the same token, if someone joins a cult where they are at risk of mental or physical harm, another person trying to point this out isn't fanatical.
Applied to religion as whole, if I believed something or other to be true because I'd been taught that it was. Somebody else pointing out inconsistencies in the teachings isn't a fanatic, they're allowing me to make a more informed decision (which may well still mean my believing in the same things, but for a different reason).
For the sake of argument, if I believed totally that it was wrong to kill/murder, based on one part of a holy text, what would be wrong with someone pointing out that another part of the same text instructs me to allow the men of my city to stone my son to death if he's rebellious?
One is a direct instructon not to kill - no exceptions, no explanation, very clear cut. The other seems to be an exemption to the rule. Surely, if one accepts either as being true, it automatically precludes the other? That said, if at least one area of the text is incorrect, who's to say others aren't? Other areas that I may have based my life decisions around. By having inconsistencies pointed out, I am better able to decide for myself what to believe in or reject.