It's all about context.
For example... 'What's the difference between a loaf of bread and a Jew? A loaf of bread doesn't scream when you put it in the oven!'
Disgusting, sick joke and I'd want to punch anyone who told it to me. As anyone might want to punch me for telling it... sorry, making a point here.

But humour has been found in the whole Nazi thing, from Charlie Chaplin onwards. Likewise, any contentious issue you care to mention. Race, sexism, violence, hatred, anything you care to mention. It's about what the comedian does with it and the point they are trying to make. You ever heard that Lenny Bruce sketch where he mentions the n-word over and over again... potentially horribly racist, but check it out, there's a point... I'll wait.
https://www.youtube.com/watch?v=gfNhiRGQ-jsStill here?
My favourite comedian is Jim Jeffries, check his stuff out on Youtube. His last live show mentioned gun / school murders, rape, racism and the Reeva Steenkamp murder. Horrible subjects... but there was always a POINT to make at the end of it about how utter fucked up and ridiculous the human race are! Offensive, possibly, but very clever and intelligent.
I think I can only offer you the BRASS EYE special from 2001, the one about paedophiles. I can think of no subject less suited for comedy but, damn, it's so clever and, yes, very funny... (please, only click on this if you're not affected by these issues... it
is rather hardcore comedy...)
https://www.youtube.com/watch?v=RcU7FaEEzNUInteresting thread.