On the other hand, when they got out in front of the movements, they would alter the course of the movements.
Alter to what? You are implying some sort of underhanded maneuvering that I not sure ever actually occurred.
After Civil Rights, Martin Luther King Jr was moving to topics of that are still controversial today - like ending the Vietnam War and ending pervasive poverty. As you say, one's the net effect of that change depends on one's prior values. More importantly, I think these types of change were organic to the movement that King was leading, not imposed from above.
Instead of imply, I'll just state that they supported movements to further their own interests, which were not identical with the interest of the followers of those movements.
I have found this most wonderful (if fairly lengthy) article, and thought you would enjoy having it brought to your attention.
It is so good, I think we should include it among the references in the "Politics is the Mind Killer" wiki page. But, before that, I submit it to you, and ask you: is there anything in this article that would warrant its exclusion from this site? I mean, besides the fact that it is about politics, and written by a notorious Social-democrat (And is that in itself grounds for exclusion?).