Paddy Irishman jokes annoy me. If such jokes were told with Ahmad, or Krishnan or Ishmael as the object, they'd never be acceptable. And the cultural group who most enjoy telling Paddy Irishmen jokes *do* have a history of pretty overt discrimination against Irish. Recent enough that my mother remembers "No Blacks, Asians or Irish" text in ads *in the papers* for rooms to let in London and that I've experienced lesser degrees of it myself in more recent times.
So no, Paddy Irishman jokes should not be acceptable, no more than jokes about the stupidity of any other group of people.
Also rather disgusting is the modern resurgence in rather cruel and nasty jokes about having ginger hair.