Take the following joke:
Q: Why are there no {
insert racial or ethnic group} in Star Trek?
A: Because they won't work in the future, either.
Is that funny?
Take the following variant - substitute "
Scousers"
Does that make it a difference?
Have we got any Scousers on here? How would they feel about the variant?
If I were a Scouser, then I don't think I would be liable to be any more or any less offended by the joke than if I were one of the relevant ethnic group. Context would be everything, too; I can see myself laughing at the stereotype in the context of a mix of wisecracks at a comedy show, but might take the hump if the joke was directly aimed at me personally, say down the pub.
But it's more complicated than that. The "wogs" and "coons" jokes and remarks in TV sitcoms of the recent past did NOT grate on the ears of a large slice of the population, yet today almost anyone would find that hard to believe. I'm sure therefore that many "wogs" and "coons" of the day must have been on the other side of that equation; it surely can't have sounded, on average, anything like as bad, or carried anything like the same level of offence, as those words have come to over the years.
It hasn't been a long time either. So now we see comedians totally avoiding those types of jokes, but still homing in on specific groups - such as Scousers. Humour based around the notion that the Irish are stupid still seems to be acceptable, but is it right, and for how much longer? I wonder whether we have reached the end of the line, or whether any discriminatory humour, not just ethnic or racial, will in due course go the same way, if society's attitudes to discrimination continue to evolve the same way? Thus, for example, jokes at the expense of fat people, ginger people, etc. may eventually go the same way.