Of course, if you look at all old advertising, everyone was caricatured -- the woman who didn't wear deodorand and couldn't get married ("Often a bridesmaid, never a bride" was the tag line for "Odor-O-No" brand), the tiny-waisted housewife cleaned the kitchen in pearls and high heels (though to be perfectly honest, my mom did this), Barney Fife made white policemen look silly, as did "Car 54, Where Are You," drunks were objects of humor, and the list goes on. The level of appeal was low on all fronts, not just on the racial front. Which is not to say I hope we go backwards -- I think a degree of refinement, sensitivity, and good taste is important at every level. I positively cringe at some of the stuff in that slide show, and I'm glad we've made strides.
As for Little Black Sambo, the story was one of cleverness, not of servitude.
And I agree with you, Mike G, that the image of Aunt Jemima and Uncle Ben suggested good food and hospitality. My dad grew up in Florida, and started working in a hotel at age 10 (when his dad died), and he would always tell me that the African American cooks were the best cooks in town. No hotel could survive without them.
Also, I just attended a program last week at the IACP meeting on the train culture that was associated with both Chicaago and the Great Migration. It was taught by a group of African American women, two of whom had grandfathers and uncles who cooked and servied in the dining cars of the old railways. They spoke of hardship, yes, but they also spoke of great food, incredible pride taken in their work, and the lifting of families from poverty up to the middle class. It was a heroic era, and one that should be remembered, not denied.