I'm sorry, but how can a minor fictional character carry that much weight?
I do know what you mean. There are times when one bad association can change my opinion of a name. But usually those are real life people. Even then, I can choose to ignore them*.
I can understand a famous literary character like
Juliet or
Guinevere taking a name over in one's mind. But is
Dolores Umbridge really so formidable?
I don't mean to harang you. It's just that I'd hate to think a great name like
Delores isn't getting due consideration because of one minor character from a children's book.
*
Imelda Marcos didn't ruin
Imelda for me.
Eamonn (de Valera) was a discredited name in my (IRB) Irish grandfather's house. But I love the name anyway. And why not? It's gorgeous.