Let's say the Imperium had the current safeguards against heresy ten thousand years prior, the Ecclesiarchy, the Inquisition, the Imperial Cult, the Officio Assassinorum, the Grey Knights, and what have you. Would they have fared better in regards to the whole Horus situation? Did the Emperor fuck up massively by trying to starve out the Chaos Gods with atheism and logic, when it all could be fixed with rampant zealotry, draconian scrutiny, and mandatory piety?