The "There can be only one true religion" statement

I'm curious on what fallacy this statement falls into. It sounds very close to a black or white fallacy but i'm not sure and i would appreciate any help on the matter.

Thanks,
RE

he statement implies there is at least one true religion. Which means it starts with the Fallacy of the False Alternative. It is possible to have other alternative answers: there is no true religion, or perhaps there is more than one true religion. 

The statement also starts too high in the hierarchy of logic. Before one can ask if there is only one true religion, the proponent must establish there is at least one, then ask if there are other true religions.

The question also assumes an unproven imperative as a premise in the clause: "There can only be ..."

These are just the thoughts that come to mind immediately. I am sure there are more errors.  

I think this is more of a philosophical question. Those who argue for this will almost certainly have a religion in mind that is incompatible with any others through mutually exclusive claims. For example, Christianity and Islam cannot both be true. What they are basically saying is that IF their religion is right, then there can only be one true religion. That is a big "if." However, those who define religion only in subjective terms (e.g., the feeling of something greater than oneself) could mean that more than one religion is "true."

I don't see any fallacy, just an unfalsifiable claim. If used in argumentation, it could be unfalsifiability , definist fallacy , or perhaps some others depending on the structure of the argument.