hhmm this all 'defensiveness' over the Black Flame seems a little over the top to me. I know about the Black Flame, have even spoken about them in game... can't recall how I know about them, or who told me... but word is out...
What I will say is that - I don't know what they are, I don't know what they stand for, I also do think that they are to be avoided... such is the Rumour of them.
Sadly, the more secret a thing is, the more likely it is to be known out side the secrecy of its group - it is a law... an unwritten law, like Murphys law *AKA Sod's law.