Seriously, their society sounds so overtly positive in the face of a preposterously hopeless and uncaring universe, there's no way even the codex is telling the truth.
It's like being stuck in a malfunctioning elevator with the Adoring Fan from Oblivion, or trapped in a burning home with Ned Flanders; the overt positivity just seems like it's projection and there is a hidden darkness element somewhere waiting to come out.
The "Greater Good" religion simply sounds too good to be true. So they should all be destroyed, and their societies wiped from existence.
Edit: it looks like many people here don't understand the obvious hypocritical irony and sarcasm written here...
I feel like having more aliens that aren't powered by evil is pretty important for the themes around 40k and the IoM.in particular. If all the aliens are as evil as IoM propaganda implies, it justifies their xenophobia, which is supposed to be baseless and reactionary fear mongering.
Exactly. And it's funny how much it makes unironic Imperium stans rage out; it shows that for them it's not about the righteousness of the cause, it's about identifying with the faction that's coded as conservative-Christian.