Stereotypical? Yes. But how is this derogatory?!?

I see many stereotypes in this film. But how is this derogatory towards African-Americans? Cartoons, especially during this time period, depict many characters, including caucasians, as slow or "Elmer Fudd-like". Why should this film be any different, or more scrutinized than others? The "worst" element in the film is wording on which midgets are murdered at 1/2 price, and "japs" are free. Again, this was made during a wartime period. I think this short film has many wonderful elements. I don't mean to sound racist. Can someone explain why this short film is so "bad"?