These very Christians do not know much about other branches of their own religion, so how can they reject them? And they do not know much about the various other religions around the world or the branches within them, so how can they reject them? Most Christians do not know enough about their own religion! All a person has to do to reject their own inherited religion is to subject it to the same level of skepticism they use when rejecting all other religions.
This represents The Outsider Test for Faith I argue. Just think what Christians are saying. They're saying that in order to reject any given religion a person must know a lot about it. How much, I ask? And how long would it take to learn a lot enough about all religions in order to reject them all? And wouldn't Jesus himself be opposed to granting salvation only to people who knew a lot about the religions of the world to gain the proper amount of knowledge that Christians require in order to find the one correct one, if there is one? Didn't Jesus come for the lowly, the outcasts, and the babes
Such inconsistency knows no bounds. No wonder my claim is that Christians demand that we prove their faith is impossible before they will see it as improbable.