THe witness claim is they are the only ones with the TRUTH.
Just give the truth some thought for a whIle. The goal post on things that are true us generally not moving. Also it sometimes may be hard to get to, but once you do its always so simple. Are those things true with this one religion?
You want to compare it to an engine, here is a good one. The fuel thay religion runs on is emotion, not rationality. Now when you are debating or making a stand emotion and fallacies are ok if you are discussing sports teams. But quite another when discussion being killed by god at the big A, guilted, shamed, or even shunned. Something of life and death and serious concequencss should not be running on emotion.