If you thought I was referring to articles author I apologize as that's not what I was meaning to say.
The problem is that the Bible is not very internally consistent. At some points it tells us to love everyone regardless. At others it tells us certain people deserve to die. As far as I can tell, there is no objective definition of what being a "true Christian" entails.
Every consistent guide to life via some religion is just going to be cherry-picked from the grander whole of the religion's beliefs and texts.
While I'm inclined to agree that unconditional forgiveness and following WWJD is probably the better Christian (well, one I'd like to share this Earth with), keep in mind the crazies also believe they're standing on solid scriptural ground.
This generalizes to just about every religion, for what it's worth...
The same can be said regarding various religions. While there is room to disagree over the scope of certain commands, or whether certain statements are figurative, or how exactly to reconcile difficult statements [1], there are certain well-attested fundamental principles within most religions which are agreed upon by diverse sects. It is not a fallacy to point out that someone claiming religion X violates its core tenets and therefore is not legitimately practicing that religion.
[0] what makes NTS a fallacy is that irrelevant criteria are being used to exclude an entity from a group they actually belong to. It is not NTS to point out that James Doohan was a Canadian of English/Irish descent, and not actually a Scotsman.
[1] in texts I've read from many religions, oft-criticized statements would be better described as "difficult to reconcile" than actually inconsistent or contradictory. The example you give is not even particularly difficult to make sense of; in the Bible, everyone deserves death, yet Yahweh shows love and offers forgiveness to all, so asking His followers to do the same is not at all surprising.
