You'd be great for that part

Well, yes it is, it can be pretty hurtful, but they want to keep the movies relative to the book in terms of characters and their physical attributes. Some people even take pride in looking like a book character, even if they aren't described as attractive

I thought maybe they boosted the actor's self esteem by taking extra time to make them look bad.

I always figured it was lind of in the job description that you would have to pit up with being the "ugly" guys or girl

I always looked at it this way, if I end up hating a character so much like umbridge, it was because she played her part so well!!