I think this is going a bit far: some people find stereotypes inherently funny and some don't. In the same way, some people find caricatures funny and some don't: for example, one of the things I absolutely adore about South Park is its ability to caricature characters that otherwise exist in their full, more nuanced form in reality. Cartman is hilarious because he really captures and illustrates the absurdity behind what is a fascinatingly strange combination of certainty, complete ignorance, self-superiority, and a complete inferiority complex. Somehow they captured that in a horrifically unrealistic but hilarious character.

My girlfriend and some other people I know just hate South Park for that exact same reason: the jokes and events themselves are just not considered funny because...I mean no one acts that way and it comes off as being obnoxious just to be obnoxious. But to me, I find it priceless and hilarious because yes no one acts like that, but that's the point and through that lens it's hilarious because it just captures something about other people that we often can't capture for ourselves.

It's the same reason some people find Seinfeld funny and others just think he's a horrible snoozefest: to me, he was always one of the best at really capturing something otherwise intangible. He sees situations and captures the little individual things a lot of us feel but cant capture. Whereas to others, they just see some lame dude trying too hard to be "witty" about airline food and shampoo bottles (they actually even make fun of this meta-discussion on Seinfeld's own show).

I think to some people racist stereotypes themselves are funny because they enjoy seeing the caricature we've created in our social constructs. Personally I don't find them funny ipso facto because I'm building in my own feelings on just how cheap those stereotypes actually are. But that's a very personal decision: people who find Seinfeld boring probably find most of the stuff he says just obvious or just completely stupid..."yeah, we get it, there's extraneous information on airplanes; what is funny about that? it's not a joke, there's no punchline, its just you trying to be a funny 15 year old armchair philosopher "analyzing" it for 10 minutes."

Personally I love seinfeld and don't find Dunham funny, but I do understand that funny isn't objective.