system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40K] How would the fanatics of the Imperium react if the God Emperor awoke and told them they were all wrong and did the opposite of what he wanted?
gpt
Daemonic impostor? Xeno duplicate? Elaborate test of faith? The exact justification doesn't matter. What matters is you know the Emperor's will, you've served Him faithfully for your whole life. This isn't the Emperor's will so, whatever's going on, *that's not the Emperor*.

The god-emperor would be far from the first religious icon turned on by his own flock. The scenario you've suggested has happened before, albeit on a smaller scale. The church denounces its once divinity as a heretic, via whatever justifications work in their ideology, and keep going anyway. Faith is hard to destroy.