Being loosely religious myself, I think the only thing potentially sillier than Bok is claiming that this story is one for the worst ever because you don't like that part of it is set in a church and/or involves (fictional) demon worship. Again, the problem only arises when people can't tell the difference between fact and fiction and end up taking things far too seriously. And given that the Master's incantation is actually just Mary Had a Little Lamb backwards, I think we're all sensible enough to recognise it's very comfortably in the latter camp.
The thing about Bok is that it's very apparent that back in 1971 he was absolutely terrifying. In hindsight, he is not. In any way. A clear antecedent to the Weeping Angels, sure, but also a bloke in tights sticking his tongue out. Also, despite watching this again not too long ago, I have no memory at all of what his role was.
Basically, episode 1 I think is one the best 25 minutes of 1970s Who, ingeniously framed in the (at the time) fictional BBC3; so while we're never going to look at this story and think it's real, we instead look and think it's the news...and the news is real. It's a brilliant way in for the audience. The only flaw of that first episode IMO is, along with the rest of the Pert stories, the Jane Austen levels of coincidence in everything happening within driving distance (and time). The rest is fairly standard fare, possibly a bit sub-. Which is a shame. It's still one of his better ones, and easily my favourite of season 8.