Most top-managers will agree that most conversations and negotiations they are having are difficult. Either a subordinate has 'toxic' attitude, or a partner is not willing to cooperate and tries to advance his agenda using manipulation techniques. This is why SoftServe's decision to have their senior-level teams to practice difficult communications was straight on point. To help training participants feel the challenge, we used real-life cases and video-analysis to practice the skills of argumentation, answering questions, and handling manipulation.
No matter how we view manipulation, it is inevitably part of persuasion process, though not the most ethical part. However, in the 'post-truth' society, the scope of and the opportunities for manipulating information increase drastically - both in social networks and in professional dialogue. How confidence helps to be persuasive in difficult conversations, see this HBR article: https://hbr.org/2015/09/how-certainty-transforms-persuasion.