When you manipulate a person's distressed emotional state to convince them into an action, even when that action is a positive one (sponsoring a child) there is always the potential that the person who was manipulated will later realize the manipulation.

Essentially - If he had convinced the crying woman to sponsor the child she very well have felt better on an ongoing and permanent basis (a positive result for everyone involved), however there is also the potential that at some later date she would have realized the manipulation.

My understanding of being manipulated is that the later realization has a highly negative outcome - I.E. making the woman more depressed than she was before the manipulation, more likely to believe that all people are manipulators (less trusting), etc.

Whenever you piggy-back a distressed emotional state to manipulate a person into an action you risk breaking that person (Causing them to stop trusting people).