Have you heard the one about the rape joke? No, I don't want to tell it either. And I suspect you don't really want to hear it anyway. What does and doesn't make "acceptable" comedy has been the talk of the Edinburgh Fringe this week. If politicians are not allowed to talk about their understanding of what constitutes "legitimate" rape, then is it OK for comedians? Are there subjects that are so offensive you'd do better to steer clear of them?

These are not questions comics should have to think about. It's a comedian's job to make you laugh. And often people do laugh at the "wrong" thing. Whether it's acceptable or not depends on the skill of the comedian and how good their material is. To paraphrase the highly inoffensive Jimmy Cricket, who was back performing at the Pleasance Ace Dome this year with 1970s New Faces winner Mick Miller ("combined age 128"), it's the way you tell them. Offence to the late Frank Carson intentional.

We're in a weird place with political correctness. Channel 4 has just scrapped its Big Fat Gypsy documentaries. Ever since the furore over the deeply unsubtle "Bigger. Fatter. Gypsier" adverts, the brand has become too controversial. It's hard to ignore the fact, though, that they've been one of the channel's biggest ever ratings hits. Audiences of more than seven million found them highly entertaining. People like things that are politically incorrect. They particularly like laughing at things they are not supposed to laugh at.

Similarly, barely a week goes by that a comedian is not berated for mocking the appearance of a spoon-faced Olympian. Or for cracking some gag which reveals how we're still secretly much more prejudiced than we'd like to believe about all sorts of things. You can't tell the millions of Jimmy Carr and Frankie Boyle fans that they shouldn't be finding the jokes funny. They are too busy laughing.

Comedy, unlike documentary, allows you to get away with a lot – and rightly so. It's non-fiction and in a world of its own. It's not real life. There's a huge gap between how we want things to be in society (inclusive, non-judgemental, equal) and how they really are (unfair, prejudiced, sneery). Comedy's job is to point that out, not ignore it, tiptoe around it or pretend it doesn't exist. Comedy should be able to talk about whatever it wants to talk about, however inappropriate.

Of course, there is plenty of stuff around that gives comedy a bad name. There are references galore to porn, rape, gypsies, "chavs" and "pikeys", not to mention the endless mentions of Josef Fritzl and Madeleine McCann you get on the circuit. One day, someone will combine all these topics and spontaneously combust. Personally, I may commit an act of violence if I hear another reference coming from a geeky young man about locking his girlfriends in the shed. But that's mostly because it often feels autobiographical and I get all maternal about it and worried for him. And them.

It's always the supposedly "offensive" stuff that makes headlines. Meanwhile, loads of new comics are quietly getting on with what comics do best: being exceedingly silly. All 10 of the top 10 jokes at the Edinburgh Fringe Festival are supremely silly and completely inoffensive. "You know who really gives kids a bad name? Posh and Becks" – Stewart Francis. "Last night me and my girlfriend watched three DVDs back to back. Luckily I was the one facing the telly" – Tim Vine. Silly, silly, silly. Everyone's happy. (And if you don't think those jokes are funny, I refer you once more to Jimmy Cricket. You're reading it to yourself wrong.)

Even more refreshingly, this year's Fringe has seen the return of good, old-fashioned banana-skin comedy. Today, the winners of the Foster's comedy awards, Best Show and Best Newcomer, will be announced. Clowning and physical comedy feature heavily. And with a record total of two women on the Best Comedy Show shortlist – Josie Long and Claudia O'Doherty – for the first time ever, there is not a bad rape joke in sight.

Not that the first-class performers on the shortlists would avoid any subject if they could make it clever and funny. It's just that these are all comedians who celebrate the art of silliness and the value of connecting with an audience. They don't need to go for cheap shock tactics or dodgy "edgy" stuff. Instead, they've spent years working on being geniuses at stagecraft. The nominees for Best Comedy Show include gloriously lunatic sketch trio Pappy's, the "deliberately eccentric" James Acaster and self-confessed "total idiot" Dr Brown, who doesn't have to speak to command an audience. I cannot even look at his beard without giggling.

As for banning certain topics? Tell a comedian not to tell a joke and they will want to tell it all the more. Much better to steer comedic talent towards idiocy. Silliness is the ultimate cure for the tedious, unwinnable offensiveness debate. What's best about silliness? It never hurt anyone. Except to make your face ache. And no gypsies harmed in the process. Bonus.

Twitter: @VivGroskop