The expression of emotion is how people navigate through the social environment.

When we express our emotions, we give others the opportunity to see if their emotions are in alignment with our own. From the emotional expressions of others, we learn who we want to extend ourselves to, and who to avoid.

Thus, people are naturally distrustful of people who hide their emotions.

Emotionally manipulative people shut down their victims so they cannot interact with others in a way that is natural to them.

It is like putting a bag over a person head.

Thus, the victim becomes isolated and dependent on the emotionally manipulative person. (More often than not, it is not a complete shutdown,.. just enough for them to be under control.)

To achieve such control, either:

1. abuse the victim so they are afraid to express their emotions, and/or
2. tell lies to the people around the victim so they do not trust, or misinterpret, their expressions.

Now, as an exercise, extrapolate this idea to a national level, where whole populations of people are bullied into keeping their emotions locked down, or dismissed as having a mental disability.