You sound just like the king of Sixty Three Nineteen... He asked us if we could not have left them alone? And I considered it... I had hoped, until he sprung his treachery upon us. He was not the King, or their Emperor at all, but an impostor, and he tried to slay my Liege Lord Horus Lupercal with a trap.

[ His eyes grow very distant, and somewhat pained. ]

And then we went into the hills to continue the compliance campaign there. What we found justified everything i have said about the dangers of gods. We found Fanes to their.... spirits. The brought daemons out into the world, turned my battle-brothers against one another, killed my men, killed the remembrancers, and almost killed me.

War is cruelty, Mamzel. We cannot refine it. But it was cruelty with a goal towards the betterment of all. We were trying to save them from Old Night.

.....

But darkness spread anyway, our leaders were seduced and tricked into falling to sorcery and worship of these False Gods themselves, and in so doing they betrayed us all, betrayed humanity, and betrayed the Emperor. The burned the galaxy, and committed the greatest act of treachery in recorded human history.

[ His eyes refocus, returning to the present moment. ]

Nature may be red in tooth and claw, but there is more than just safety in numbers. Gatherings of humanity have created more than just tribes and wars. Art, culture, books, science. These things were made with empathy, to help one another.