Honestly, I find the satanic slant of the Cathars(something that PC historians tend to ignore) very interesting.
What's ignored? There isn't really any "satanic" slant to Catharism (and Satan being ill-defined in general).
Satan isn't ill-defined at all.
Cecil mentions the "Gospel of Truth" in that interview. It is one of the main texts used to attack the gnostics, both before and after the rise of Catharism. You see, they believed in two gods: a lesser god, earthly, evil and opressive(The "Demiurge") and an enlightened god, the one that offered salvation through... knowledge. Now, the orthodoxy obviously shunned these heretical views, but there was more. This division between two "gods" and some of the characteristics of the second "god"(the one they worshipped) was what lead Saint Dominic and others of accusing them of devil worship before the Albingensian crusade.
And it makes all the sense in the world really. "Lucifer" means "Light bearer" after all, and the tempting serpent at the garden of Eden("Lucifer" again) used offerings of knowledge and power to deceive humanity. The symbolism is clear. Couple that with the gnostic belief that knowledge and enlightenment would lead them to be "as God" and you got the picture.
Most of the favorable depictions of Cathars(and gnostics in general) you find nowadays are really wishy-washy. Much of our knowledge about them might be biased and exagerated, but their shit was obviously crazy.
BS3 was a piece of crap with a retarded story and idiotic push-the-crate puzzles. I reluctantly gave BS4 a try and got bored after half an hour and dropped it.
You saved yourself. It was even worst than the third.
The story involved a Vatican sub-mafia plotting to wipe out "non-believers" using a majistical anti-matter machine. You couldn't make that shit up. I don't remember quite well, but apparently it was based on some other Dan Brown book that had a similar plot. 3 and 4 suffered from that double fail, bad gameplay and bad writing.
Imho, one of the reasons 3 and 4 failed was that they tried to capitalize on the Dan Brown shit(the original game was often compared to it for some reason) and decided to replay these Templars/Gnostic conspiracies. I'm really disappointed they will do it again.