We have evidence that the narcissist knows he is mistreating you as we reflect on his deceptions and the many other ways he hides his bad acts. The term used in a criminal court is "consciousness of guilt". A person gives evidence of their awareness of the wrongness of their acts by their attempts to hide them. This concept is concrete enough to be used as evidence in a court of law, so it is concrete enough for us to use as evidence to convict our narcissist.
The narcissist seeks targets of opportunity. You are abused by him because he thinks he can get away with it. To deliberately use, abuse, hurt and obliterate someone just because you can is evil. Those who argue that this doesn't mean the narcissist is evil make a good point. They say it isn't about you in the narcissist's thinking. They don't even see you so how can it be calculated evil? While there is some truth to the fact that the narcissist ignores your humanity I can't completely buy into this theory. The narcissist gives it all away when they lie and cheat to get their way. If they truly didn't "see" you then there would be no reason to create a false reality for you in order to obscure truth. They know they have to deal with the fact that you are a separate (from them) human being with a mind of your own, so they have to be aware of what they are doing to you. He has found a way to exonerate himself from the label of evil in order to continue doing what he does. Are you willing to exonerate him too? We become his slave if we do. What the narcissist does to his victims when no one is looking is evil. He knows this on some level which is why he projects his evil acts off of himself onto others in an effort to distance himself from that which blackens his own character.
The narcissist works to completely obliterate you as a separate human being. Her goal is to assimilate you. Make you an extension of herself. This is what justifies her using you. You've been transformed into another of her body parts that she gets to use at her will. You have no will of your own she has to consider. You have no needs or desires separate from her own. The way this assimilation is accomplished requires evil acts. To maintain this relation to another human being requires ongoing evil acts. It is a form of cannibalism. In my understanding, cannibalism is always evil. Even if the cannibalism is only psychological. Who you are is defined by your mind. To consume who you are....how is that not cannibalism?
Because I believe in the existence of evil I am able to work to avoid doing evil. To avoid doing evil is to avoid being evil. Goodness in people is never an accident, in my opinion. Good character requires decision and effort. The easy path is the evil path. Good character means we practice self-denial when necessary, we consider the feelings and needs of others (sometimes at the expense of our own), we live in the truth (whether good or bad), we conduct ourselves honorably whether or not someone is looking. If we aren't allowed to call evil by its right name then we really are not able to credibly give honor to goodness. To do away with one is to do away with the other.
If we can't say that deliberately hurting someone is evil then we dis-empower victims of evil. They have no real name to attach to their experience or their abuser. Pop psychology doesn't believe in the concept of evil so victims of narcissists are left to assume the abuser doesn't really mean to do what they do, or they have to excuse the abuser on the basis of the abuser's own "damage", and they have to minimize their own experience and blame themselves. This makes it very hard to pull away from the abuser because we are left to believe that in some way we are the problem. The abusive narcissist is quick to tell us that is so because he is quick to use pop psychology to exonerate himself. He's not insensible when society hands him a "get of of jail free" card. He grabs it and runs with it. Combine pop psychology with a narcissist and you make him worse. Research is bearing this fact out.
Calling evil by its right name allows the abused the opportunity to see valid reasons to get away from the evil that ensnares them. An acknowledgment that evil does exist is directly related to the concept of freedom. As long as we don't call evil by its right name we are entrapped by it. Emotionally, mentally, even physically. We are slaves to someone's will. Call evil by its right name and see the path to freedom open up in front of you.