re: cults
I would refer you to The New Shadow. Cults were very much on the authors minds towards the end. At the very least, it was on his mind when he was considering the story line for NS.
I was under the impression the BW traveled east to "persuade and inspire" tribes/nations of men to not listen to and fall under the sway of Sauron's influence. Without the counsel of the BW, Saurons human legions would have been much larger than it already was. IMO, i could see the BW falling under their own desires to control the minds of men, especially after dealing with them for thousands of years.
"Saruman Light", if you will
