Monodominance is interesting - The 'founder' was a pessimistic old bastard who, after years of service, thought humanity could only survive if everything else was dead. Only later Inquisitors decided this was an aim rather than a grim statement of fact. And, if you look at it, that's more of an anti-Xenos and daemon statement. You could strain it to anti-mutant, perhaps, but it's very outward looking. Yet Monodominants (as they are portrayed) tend towards the Tyrus/Muundus role, very much focused inwards.
Monodominancy clearly existed before the name; it's the Imperial creed, really. Kill all the aliens, we're better. Every radical is a Monodominant by that definition – even Xanthites and those who use only alien weapons are using them against their own creators/kind. To question mankind’s supremacy is to question one of the founding concepts of the Imperium, laid out by the Emperor himself (and in this case, actually genuinely). To consider it unobtainable, like Goldo himself clearly did, would be a milder blasphemy, but common enough amongst older (more powerful, experienced and influential) Inquisitors for them to get away with it.
The opposite of Monodominance is heresy, pure and simple.
Of course, the basic idea is very, very different (as I mentioned early) to how it is practised within the faction. It clearly was adopted by some very charismatic extreme puritans, giving their own creed (of overzealous Puritanism) which had existed as soon as the Imperium settled into its current shape after the Emperor’s death, a name and perhaps more of a sense of common purpose.
The name is very much pointing out the obvious, and of course anyone who opposes Monodominants can be accused of opposing Monodominance itself, which is heresy. I find that rather fitting.
Skoll - I like to focus of the moral qualms of Inquisitors as well. Dorian has them, as you know, and a character originally planned to appear in AM (who probably won’t now) is a former Inquisitor who had a crisis of conscience and went into hiding. Essentially, I think an Inquisitor either ‘gets over’ their morals or is eventually destroyed by them. AM’s later, mostly unwritten stages, focus on Inquisitors whose arrogance has catapulted them into extremism (an extremist Istvaanian hiding in plain sight, a Xanthite driven mad by his daemonsword and a Monodominant, being an old crone, who acts entirely behind the scenes with disturbingly black and white morals that would make Tyrus balk) and Dorian’s own crisis of conscience.