Well, you said that the word narcissist is useful because it helps people identify abusive parents. Which would imply you think there's some connection between being an abuser and having NPD. So the fact that you think a mental disorder is responsible for abuse is an example of that systemic, oppressive otherization that we narcissists experience. I was told by a former friend that I don't deserve to live, because narcissists don't have a shred of humanity. Is that not oppressive otherisation to you?

I agree that it's not desirable to conflate the two in common usage, but I don't really see how that can be done while continuing to use those specific terms.

What constitutes toxic behaviour is culturally subjective. Many people in the first group would have been considered a part of the second not so long ago.