People who think they know better or have right on their side are likely to use whatever persuasive techniques they can to move people to their position. They are often selective with their facts and persuasive with their language.
Take Cable news hosts/shows, from both the left and the right. They continually use language and choose stories/commentaries that tell their viewers who to fear, appeal to their patriotism, to denigrate politicians of the opposing view, and to sensationalize the truth so as to increase ratings or drive the political agenda. And they make a lot of money doing so.
When Princeton review first started growing and teaching lots of kids how to take the SATs, they often taught students how to find the experimental section and had them purposely miss every one of the questions. This would make it easier for future test-takers without providing any real benefit to the students themselves.
Religious leaders are some of the greatest manipulators in history. Many of the popes were certainly effective in changing the course of history, and names such as Cardinal Richelieu remain infamous. Certainly, many of us yet remember such evangelists as Jim and Tammy Baker and Jimmy Swaggert who had people contributing millions to them.
While many have their own personal gain as the goal for this manipulation, there are those who genuinely wish to lead people to the life that is good in the manner which their particular sect defines this word. While they should not be manipulative, sometimes they feel that slight manipulation is justified in the benefits it produces. For instance, inviting a person to the church supper or other secular function may ignite that person's interest in attending the religious services later.
I agree with post #2. I frequently use manipulative language to get my students to think more and work harder without actually realizing it. In the long run, it is usually beneficial and often students come back to tell me they figured it out.
I also witness students manipulating each other, teachers, administrator, and even the law, for the benefit of their friends and peers. I've experienced several accounts of students lying to protect a friend (or even an aquantence) at the risk of their personal benefit or for no personal benefit at all.
Teachers and coaches try to manipulate students/players all the time. We do it, I hope, for the good of the student.
Teahers and coaches will both try to push their students and to motivate them. They will (hopefully) think about what they say to their students and how they say it. They will try to say things that motivate the students to work harder. The coaches and teachers don't really get anything out of it. Instead, they are trying to get their students to care about and to improve their own performance.