Fear is a powerful emotion. I cannot imagine how it would be to live a fear-full life. Living in fear and worry changes you. It effects you physically. It can make you sick. It also changes relationships. ALL your relationships.
Fear in the hands of a Narcissist or Histrionic is worse. The only way they know how to allay their fears is to try to give it to someone else, or to you if you are in a relationship with a person like this. And they will try to give it to you by any means possible. Anger, threats, manipulations…pick a methodology. The one way that they cannot allay their fears is with the truth. The truth of the fear and how that person became that way. Because it might involve the taking responsibility for actions, past and present. Or, coming to terms with difficult personal truths.
We all suffer. We are also all the cause of our own suffering. We choose to accept that fear (or anger or hurtfulness) from others.
Choosing to not accept it, however, does not mean all out rejection of a person who is likely in far greater pain than you will ever be. It means acting compassionately towards them in a way that is also protective. How to do that is as unique as every person on the planet. This is why we sit.