Why is everyone demonising her for hating Knocked Up?

Ironically I think it's her best film. I know it has loads of stereotypes, but I've always found it to be funny and entertaining.

Yes, every actor has at least one movie in their catalog that they hate. But most actors don't talk publicly about how much they hate that one movie until years after its been out, if not decades. They don't usually tell the press about how they hate it during the PROMOTION of the film's RELEASE. Especially when they are also implicitly making accusations about the writer/director of the movie, when the movie is supposed to be their big break in Hollywood, and that writer/director was the person who GAVE them their big break.

I think in part because it is usually stupid when an actor decides to shit on a film they got paid and agreed to do. It wasn't like someone held a gun to her head and forced her to make the movie, nor was it some movie made by a secretive director that refused to allow actors to read the script before signing up for the film... in short she knew what the film was and agreed to do it... the right thing to do is support the movie you were paid to be in or at the very least just not say anything if you didn't like the final product... Never good to go on a monkey flinging shit rampage about the movie.