Surely is a distinction between jokes based on demeaning stereotypes (the Irish are drunken, fighting thickos who love to bomb people) and cheap ridicule and observational humour (which yes, can be cutting and to the point about a person/group/nationality etc). It's not "political correctness gorn mad" to find some jokes cheap, distasteful and perpetuating of harmful negative stereotypes.
There's also a distinction based on who tells the jokes. "Right on" social justice "types" who are English telling Irish jokes in the 70's were, well, not as right on as they might think. I will listen to any Irish person tell an Irish joke. Or a Scot. Or someone Welsh. Or, well, pretty much any other nationality apart from English people. I am about as far from a tricolour waving Irish nationalist as you can get, but I don't like to hear English people say demeaning things about my country.
I don't like English people telling jokes about Irish people being thick because, to be honest, I've come across this attitude to Irish people in real life. My driving instructor, bless him, seems to spend part of every lesson telling me stories about quaint/rowdy/drunken/stupid Irish people he's met matched with a knowing nod and "you'll know what I mean..". I smile and nod because he doesn't mean it and he's a good instructor and yes, because I would look like a total twat if I challenged his easy stereotypes. He doesn't mean it as banter, either. However, people who think that there isn't significant negative stereotyping of Irish people still at work in parts of the UK are a bit blind. The people who think that these jokes are harmless - or that woman driver jokes are harmless - believe that really, it means nothing because 'no one thinks that way nowadays'.
But they do..
Obviously, I am far more outraged by "jokes" about learning disabled people. Frankie Boyle, for example, is a twat. You can laugh at him telling jokes about the Scots til the cows come home but if you find yourself tittering at his jokes about people with Down's you are complicit in it, I'd say.