Offense and humor are usually bedfellows, or at least congenial, sugar-borrowing neighbors. Lenny Bruce, George Carlin, and Monty Python all employed “shock and guffaw” tactics to expand our notions of funny while smashing through barriers of accepted behavior. Apparently believing himself to be firmly of their camp, Sean Cunningham wrote the two-hour test-of-spirit “God Hates the Irish: The Ballad of Armless Johnny,” now at the Rattlestick. That his material offends without amusing may mean one of two things. Perhaps this reviewer just isn’t ready for yuks about Ethiopian rape victims and now I can reveal myself as a prude. Or perhaps Mr. Cunningham just can’t crack enough jokes.

We first meet Armless Johnny (Bill Thompson) trying to play ball with his Da. Being armless is always tough, but in Northern Ireland, it’s murder. After his Da hangs himself from the shame, the Protestant cops frame his mum, and soon Johnny’s whole family hangs by their necks from the clothesline. Aided by a well hung, alcoholic priest (Remy Auberjonois), Johnny leaves for America. Along the way, he stops off in England to meet his true love, kill her parents, watch her kill the Queen, only to lose his own family jewels to the vicious cops who have followed him from home.

His next port-of-call, Ethiopia, convinces him his lot may not be so bad after all. After meeting (and mocking) a young woman whose misfortunes outstrip his own, a falling food packet from America knocks her dead. Listening to a song and dance from the local American do-gooder convinces Johnny that even Ireland looks better than the U.S.A. If he can just figure out a way to pleasure his girlfriend, who patiently stirs the potatoes back home, he might just have a chance at happiness after all.

Some of the trouble is context. This sort of snarky swipe gets a lot of airtime during the Fringe Festival, where musicals about menopause and the Kansan educational system abound. There it might have seemed like high spirits, rather than mean ones. But even the Fringe put up “Jonestown: the Musical,” which tried to get comic mileage out of a mass suicide. Maybe tastelessness tastes bad wherever it is. In a way, this show provides a sort of service. It experiments with a variety of different topics and points out which ones just can’t be amusing.

Director Will Frears leaves things as slapdash as he can. Having once directed “The Ballad of Armless Johnny” at the Yale Cabaret, he seems to be trying to recapture an amateurish “let’s put on a show” groove for this production. His production staff is not always with him. Robin Vest’s set looks like a vaudeville stage that’s been flooded a few times, but the grotty vibe doesn’t quite match Camille Benda’s well-polished costumes. Songs by Michael Friedman do pep things up a bit – the composer himself lurks at a piano onstage, wearing a bowler and waving flags whenever the location changes. More could have been done with – and for – him, though. The show doesn’t milk enough fun out of the musical numbers, even with choreographer Jim Augustine keeping them well supplied with “jazz-hands.”

The thing about administering shocks is that they should be short and sharp. Mr. Cunningham tends to sit on his jokes as long as he can. If one mention of masturbation is funny, then surely an entire scene about it will be hilarious? No. The best moments are the ones that have a bit of the vaudevillian patter to them, like when cops Anne Bobby (did they pick her for her last name?) and James A. Stephens do a brisk exchange on bigotry. “The Irish are dirty.” “That’s the French.” “The Irish are stupid?” That’s the Polish.” “Oh. Stereotyping is hard.”

Mr. Auberjonois has more razzle-dazzle than the others, and he also has the best scene. When poor Johnny languishes in jail, a vision of Oliver Cromwell, prudish avenger and Ireland’s bane, appears before him. Suddenly all the weak prods at the English (They inbreed! They walk funny!) turns into an angry slash right at their sense of virtue. Cromwell both shut down the theaters because he thought they were offensive and put Irish children to the knife. Suddenly my own sniffy attitude and raised hackles started to bother me – doesn’t ease at taking offense lead to ease in giving it? Unfortunately, this scene soon gave way to a longer, unfunny scene and all that good will drained away. The lesson is a good one, though. Now if Mr. Cunningham can just make us laugh while he teaches it to us.

Until April 24 (224 Waverly Place at Seventh Avenue, 212-627-2556).