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human
[Warhammer40K] How would the Imperium react to a powerful AND pacifistic and helpful faction?

 

Let's say that, in their exploration of the Galaxy, the Imperium finds a peculiar planet.  
On it, people of ALL races, xenos and humans, are living in harmony, with no war or dissense to speak of. Their leaders are "ascended" entities incredible powers, who are incredibly moral, "good", merciful and empathetic, while also being VERY neutral and pacifistic. These entities (who used to be mortals, humans and xenos alike) are pretty much all-powerful, immortal and nigh omniscent, while also being 100% immune to chaotic taint and corruption, and they freely teach anyone how to become one of them (the process involve getting rid of all mortal desires, reaching absolute serenity and purging all hate, greed, xenophobia, etc).

This planet pretty much welcome the Imperials with open arms at never oppose them in anything. Even if the Imperials attack them, the "ascended ones" simply resuscitate their victims and carry on with their day. Even if the whole planet is subject to Exterminatus, the ascended put it back, and if the Imperials try to take some people away against their will, those people are istantly teleported back to the planet.  
Think of this faction as an "immovable object". The Imperium pretty much can't do anything to them, but they won't do anything to the Imperium either, except offering to teach them their ways.

How would the Imperium react to this faction?
gpt
They would attack them, and then keep attacking them when they come back. Exterminatus and all. 

They are guilty of heresy and harboring xenos. The Imperium accepts no response to that except fire and death. 

That it doesn’t actually end up doing anything is irrelevant — war and futility are pretty much the Imperium’s watchwords.