There are many kinds of lies, and many kinds of manipulation. Some are healthy, some are unhealthy, and it takes a fair measure of skill and knowledge of the other person to tell them apart. Honesty is the first order approximation to the best policy, but is not the best policy.

I'd agree - if one "side" doesn't have all the facts - it's harder for them to make an accurate prediction and an effective negotiation and thereby come to an optimal "win".