According to the couple responses to the link that I recently posted, my impression is that most people believe that being nice is not only a way to get a desired result, but that it can play a part. There was an interesting response that was slightly bothered by the author's tone. It never occurred to me that the author may have been jumping to dramatized judgments about someone, but re-reading the article after reading the responses changed how I read it.
I see both sides (the author's and the responder's), however. I do believe that there is a certain way that people act when they want something from someone, and this can come off as manipulative, but I also believe that as human beings, we can't really help that, and we are made to adapt how we act in certain situations.
I wish that it was more natural to act exactly how we were feeling all the time, instead of changing how we treat people to get a desired result, but this might be an unrealistic hope.