I see manipulation as any other social tool - it's the intent and use that determines the good or bad. Just as a scapel may be used to heal or hurt.A baby manipulates with its cry to get its needs met - good.To me, it seems that selfishness at the expense of others is a foundation of evil, whether expressed through manipulation or any other medium.Manipulation that is win-win would be acceptable in my book. But then, I see love as being the most powerful form of manipulation - truly cherishing and accepting someone, even while not agreeing with their choices can be very powerful. It was when my Mom did it to me. :DEnjoying the conversation - you've good observations.
The secret is not to get caught up on form or the masks people wear. A little practice and seeing hearts is so much more satisfying, although not as much selfishly fun. It's much harder (in my opinion) to manipulate or use someone once they've been recognized as a mind and heart, instead of a face and world-mask.