I read this thread, and personally I consider Geiger to be a good player with great posts most of the time, but in this case I think you're a bit off, man. Hear me out.
The thing is, if you want to play the "Religious extremist" there is a class for all alignments. For LG there is paladin, for NG,CG,LN,N,CN there is the divine champion, and for LE,NE,CG there is blackguard. A lot of people seem to think you have to worship evil outsiders like devils and demons for BG, but an evil Deity fits the requirement too.
In this way, you are never restricted by the alignment, but if your looking for a rigid gamestyle, then Paladin is the way to go because there is no wavering in their alignment. They can get by with patrons of LG, LN and NG but they themself have to be LG. I don't know about how PotM treats cases like Sune Firehair (a CG deity with Paladins amongst her followers) or other exceptions to the rules. Nearly every religious fanatic concept can be made. With cleric, blackguard, divine champion, and paladin and all the multiclassed combinations. You are not restricted one bit for any concept, just need to think about it. (I just wish we had favored soul, how I love that class)