I would hesitate to compare or to put manipulation on par with brainwashing...as they are, in fact, different. Whereas
brainwashing is indoctrination,
manipulation is managing and influencing something. So, I cannot really agree with you when you say that manipulation is
a person forcing his or her own beliefs on another.. Please forgive me if I have misunderstood you...
I am bit confused by your post -- one moment it seems as if you are saying that the Ring and Gandalf (to an extent) and Saruman are forcing their beliefs upon people, then the next moment you say that the Ring and Saruman offer people what they most desire (and, in so doing, they play upon those desires)...which is it? Because these two things that you describe are hardly synonymous of each other, for how could appealing to the wishes and desires of one's heart compare to indoctrination?