Good comedy is, of course, all about being edgy and subversive, mocking widely held beliefs and holding a mirror up to ourselves so that we can confront uncomfortable realities we prefer to ignore.


There's nothing wrong with a gag being offensive. And a good comedian has a positive duty to deal with subjects such as race, religion, politics, minorities, sexual relations, sexuality, gender balance and even the great unmentionables such as paedophilia and terminal illness.


But the jokes should also be funny. Tommy Tiernan's latest rant about Jewish people, the holocaust and anti-Semitism is not the sort of "reckless, irresponsible and joyful" lunacy he says is the soul of a comedian operating "within a protected environment … [where] people know that nothing they say is being taken seriously".


It is hateful, revolting and insupportable on any level. It is also probably illegal.


Tiernan, who was speaking publicly at the recent Electric Picnic festival and who was applauded by the audience, has a track record for offending everyone from travellers to people with Down's syndrome. This time, he has crossed a line so far that a transcript of what he said needs to be investigated by the gardaí to see whether it breaches race or incitement to hatred legislation.


Those who offer Tiernan a stage and a fee also need to ask themselves whether this unfunny person is worth a platform.