The religious are bad enough already, with the BBC suggesting to them (via Being Human) that to perform an exorcism they need to kill somone (to "open a door"). Religious people really do believe in all that sort of nonsense - and kill people over it. Though it's notable that the real life ones tend to kill the victim they are (mistakenly) trying to exorcise of a possession rather than killing some extra person beforehand.

I haven't been following along, so I don't know what the supposed justifications were for the other blood baths mentioned in the bit I did see. But it's very irresponsible of the BBC to make up new bad ideas/rules for the religious nutters to follow - as if they didn't already have enough bad ones of their own.