I watched that damn video a grillion times and I always took it as he was addressing a caller who called HIMSELF "Reverend X".

Its hard to tell by the clip because there's a sort of edit I think, but after he says "Reverend X" (and he even says it like a sort of question like when someone tells you their name and you think they're bullshitting) he starts challenging dude to say his first and last name. I always took it as he was challenging dud to say his real name, not Reverend X.

Maybe you can find that out.