Se == dealing in terms of power, completion of tasks, rather than data or semantics. Blindness to Ne semantics may be used to manipulate them into Se execution of a task they don't realize is against their best interests.
Weak Ni also makes for decreased skepticism in the manipulator's intentions and less deliberate efforts to protect one's existence.

Fi == greater sense of trust when the "manipulator" has won him over. Lack of Ti may result in decreased cynicism in the manipulator's real motivations; however, as Fi can also be used to sense a person's true intentions, the manipulator must make an effort to develop a strong sense of trust from the person.