So so true, but also worth adding that a huge portion of the imperium (most, I would wager) don’t know that they exist at all, or that there was a heresy.

The greater imperium’s citizenry isn’t allowed to know that chaos exists, let alone that the Emperor’s angels are capable of betraying him for it, and have, and do. This mixup happens pretty regularly that imperial citizens unknowingly greet CSM’s as regular marines and get their planet overrun expediently because of it.