The last thing BR is, its campy. Do you people even realize what camp actually is?
The film does have silly moments. Undeniably silly, particularly the entire Penguins-On-March section. But the film is also laced with a satirical tone (not more evidenced than the "tomatoes and vegetables" comment), which aids those silly moments (OK, maybe not the penguin march...).
And yes, BR is the darkest Batman film - not only darker than B89, but arguably darker than TDK (if only so slightly). As others have stated, B89 is crime noir, but BR's goth, coupled with the imagery, and overall tone, help make this one of the darkest blockbusters that have ever been unveiled at summertime.