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To convince someone that they are lacking a product to be happy, for the sake of discussion, is the same as telling them they are unhappy. What if this person was already happy before hearing the ad? Then it becomes manipulation.

With persistence and repetition people would start to believe that their lives are not what they are supposed ro be. Another point is that they offer their products as a solution to low self esteem, confidence and whatever someone believes he lacks.

Indeed. The other side of the equation is people tend to be overconfident of their actual abilities. So for these people, their self esteem is not always built on solid ground. They are prone to "attack" in this manner.