Well, I have just had a flick through the sourcebook looking for inquisitor Goldo, and found that the authored the first treaty on monodominism. I'd like to incorporate this, so rather than having the "true" monodominants, I'd like to go with Kaled's suggestion, and name them the Goldoians. Anahilists, purists and excisionists seem to make up a good names for their respective proposed factions.
As for the faction that uses fear, I'm not sure whether this is technically correct (conjugate the verb!), but Timorians sounds like it might fit, as I gogle translated fear into latin to make up for having never learned latin in school, or been bothered to learn it outside.
I reckon that maybe Goldo's original treaty could have been copied out by his acoloytes and contacts within the inquisition, but parts of it been either changed/lost/mistranslated, which along with the ambiguity associated with human interpretation, would have led to the factions seen today.
The central tenets of the monodominant faction could be summed up thus:
1. It is the right of humanity to rule the galaxy, and this is the will of He-on-Terra.
2. It is the foremost duty of the inquisition of carry out the will of He-on-Terra.
3. Humanity must rule the galaxy alone.
4. Any who will not yield to the divine right of humanity must be destroyed.
5. No opposition to His will may be tolerated. Failure to comply means death.
If you feel I am missing anything, and/or would have any other tenets to add, please do so.