This led to the following exchange:
A lot of his cartoons were stupid, weren't they?
P.S. I think you forgot racist and sexist.
From the LA Times obituary:
John Callahan dies at 59; politically incorrect cartoonist was a quadriplegic
Two Ku Klux Klansmen heading out at night in their white sheets. Says one: "Don't you love it when they're still warm from the dryer?"
A beggar in the street wearing a sign that reads, "Please help me. I am blind and black, but not musical."
A sign in the window of a small, street-side restaurant says: "The Anorexic Cafe, Now Closed 24 Hours a Day!!!"
An imposing woman glares at a small man and says: "This is a feminist bookstore! There is no humor section!"
A small boy and his father look at a dog lying on its back with a large shard of glass embedded in its chest. "How much is that window in the doggie?" asks the boy.
Callahan was not swayed by hate mail blasting him for being racist, sexist, ageist, sick, depraved and disgusting.
My favorite features two store-front businesses: A Tourette-Syndrome clinic with a neighboring pet store advertising a 90% discount on all parrots.
I'm not swayed by racists who think they're not racists. I could've kicked Callahan's butt in a debate just like I do with everyone online.
These examples are probably among his best known cartoons because they're decent. As I recall, about half his jokes were good and the other half were stupid and sophomoric. Such as the "squaw-tistic" joke above.
The black and feminist jokes are arguably about the stereotypes. They arguably don't use the stereotypes to insult blacks or women in general. That's the difference you seem to have missed.
The "squaw-tistic" joke isn't a commentary about what Americans think about Indians. The cartoon shows a white man describing an actual Indian girl. The girl is dressed stereotypically and the man uses a vulgarism without irony. There's no "humor" except the semi-racist epithet.
What's the funny part: comparing being an Indian to having a developmental disorder like autism? Ha ha. That isn't just unfunny, it's insulting. It's a not-so-veiled way of saying Indians are inferior.
Show me a cartoon where Callahan spoofed a black person in a similar manner. For instance, a doctor returns a black girl to her parents. "She's not a ninny," he says, "she's a pickaninny!" Again, no commentary on people's beliefs about blacks, just a straightforward use of a semi-racist epithet.
I guess these subtle distinctions are lost on Boobus Americanus--i.e., people like you who think the Three Stooges are funny. To this type, racism seems to be okay as long as it's the form of a "joke." Have you ever seen an example of ethnic humor you found offensive?
For more on the subject of "harmless humor," see Ethnic Humor Suggests for MTV, Irish Band Is Just Harmless Fun?, and Deadliest Warrior vs. The Dudesons.