Depends on which side of the fence people are on. From the outside, to the viewers who get to see every side of every situation she does come across this way, however from the POV of the other characters, this is far from the truth.
From Lukes families side, she is the devil. She forced their son to switch schools from a football powerhouse to East Dillon. She talked the mother of Lukes child into having an abortion.
She has made countless decisions that have upset member of her own faculty, namely the football team.
As a principal she was obviously the bread winner for that family and decided to put her moral beliefs in priority over her familys well being by refusing to appologize and then stepping down in her position. Morally a mistake wasn't made, but because of her decision, her family did suffer from bullying and will suffer financially in the future from her decision. It would have been a cop out for her to just stand up and applogize...just wouldn't have fit her character.
I don't see a problem in having a character that is strong willed, who sticks to their morals regardless of the outcome. I think these characters exist in most TV dramas (look at Gil Grissom from CSI..a different type of character, but never one to go against his morals).
From 20,000 feet up, she does the right thing, but in the universe of the show every decision she is making is usually pissing some one off.