People have sympathy for the mentally ill. Why no sympathy for people with NPD?

Why is NPD treated as a "demonic" condition and those who have it are seen as monsters while empathy is encouraged for all other mental illnesses.

The excuse that "people with NPD treat others horribly" doesn't work for me because in my experience people who have other mental illnesses can also be pretty awful to others. My father has depression and OCD and he can be pretty awful honestly.