One of the big reveals of the Horus Heresy series was that the Imperium was not always religious, in fact it was meant to be an atheist empire free from dogma. The horus heresy has always been called the horus heresy, but it seems a little strange now with this new atheist information. As far as I am aware, none of the rebels has yet to be called a heretic in any of the books. The book series is obviously called the Horus Heresy series.
So any thoughts on this? at what point is it going to be viewed as a Heresy rather than simple Rebellion?