Awww.... DA, I LOVE being called stupid and worthless! :-P I think words like that help with dehumanization and feeling like an object. I love to feel like property, only an object owned by my Master for His amusement.
And in terms of vestiges of truth- if you need to feel some truth behind a statement for it to be more powerful- I think it is possible with these types of words. For instance, the word "stupid", besides the general connotation, if I really need to feel some truth behind it I will think of how stupid it is considered, as a woman, to stay with a man that beats and degrades you. Often with enough abuse and humiliation of that kind combined, with my thoughts about its vestiges of truth- I can be brought to tears. Delicious.