I am of the very firm opinion that, unless what you like causes actual harm to others or yourself, you should never feel guilty for liking anything. This motto for life will come as no surprise to anyone who's ever seen my DVD collection (which proudly includes the Ron Howard slushfest, Parenthood) and music collection (yes, that IS a Four Non-Blondes album you're holding there, what's your point?), both of which are unashamedly forced on any visitor who makes the mistake of stopping by. But even I can admit to some pangs of conscience for loving one particular film: Trading Places.

Trading Places is, by some measure, one of the funniest films ever made, and certainly one of my absolute favourite movies of all time – but it is also, undeniably very, very wrong. First and foremost, there's that, shall, we say, "blacking-up awkwardness".

For those who don't have this movie saved on their mobile device so they can watch it at a moment's notice, I'll refresh your memory: for various reasons that we don't need to get into here, Louis (Dan Aykroyd), Billy Ray (Eddie Murphy), Ophelia (Jamie Lee Curtis) and Coleman (Denholm Elliott) get on a train in disguises.

The disguise Aykroyd chooses for no reason whatsoever is … that of a Jamaican stoner, replete with bad accent, dreadlocked wig and, yes, full blacking-up make-up. Now, I adore Aykroyd but it is impossible to watch this scene without wincing and wishing dearly that Harold Ramis had been on set to rein in some of his friend's excesses, as he did on Ghostbusters. Lord only knows what Murphy was thinking throughout this scene as he and a blacked up Aykroyd lark about in a train carriage together – although seeing as he had recently made 48 Hrs, in which Nick Nolte refers to him as "Watermelon", this may well have felt par for the Hollywood course for him at the time. Which, sad to say, it kind of was.

Next, Jamie Lee Curtis's character, Ophelia, the classic "tart with a heart". It's such a clichéd role, and so unnecessary, too, because there is no actual reason for this character to be a prostitute, beyond the vague and queasy suggestion that such a job makes the character sexy. But worse, it's unimaginative, which is odd as the rest of the main characters break out of their tropes delightfully. Ophelia, however, remains a tough-talking-gum-snapping-tender-hearted prostitute who is predictably fond of her flashing her breasts (this being a 1980s Jamie Lee Curtis film, it was the law that Curtis go topless at least once).

Speaking of Ophelia, she is also yet another example of what feminist writer Katha Pollitt dubbed "the Smurfette Principle". This refers to a film or TV show in which there is just one woman and several men, and the woman's role is simply to look pretty and be rescued by the men.

To be honest, many of my favourite 80s films illustrate the Smurfette Principle – Ghostbusters and The Princess Bride, for example – so I'm pretty accustomed to stomaching this flaw. It's definitely not a dealbreaker, but it is a little irksome.

And finally, the end when the villain (played by Paul Gleason, who made a career out of playing unpleasant characters in some of the decade's most enduring films, including Die Hard and The Breakfast Club), is condemned to a life of being raped by a gorilla. Yes, raped by a gorilla. As a kid, when I didn't quite get what was going on here, I thought this was hilarious. Now when I watch the film I think, "Raped by a gorilla? Is that funny? Kind of? Not really? Oh well. Oh look, it's Eddie Murphy back on-screen again, thank god."

So that's the (fairly damning) case against Trading Places. How, you may well wonder after that rant, do I justify watching it several times a year? Well, Chris Rock has a great sketch about why women dance to brutally misogynistic rap music: "If the beat is right, she's dancing all night," grins Rock. This, I suspect, explains my ongoing love for Trading Places. Yes, it's got wrongness in it, but it is also very, very funny. And if that beat is right then – sorry, values! – I'm dancing all night.

First, there's Murphy. I don't care what anyone says about Murphy now, and yes, I know he has made some godawful films since his 80s heyday – but for that heyday alone he has my eternal loyalty. He was by some measure the most talented comedian to emerge in the 80s – he had to be, just to break through the racial barriers at the time – and managed to be the biggest comedian of the decade when blacking up was still seen as a laugh-guarantee.

For God's sake, even Aykroyd's character – the good guy, mind – refers to Murphy's character at one point in Trading Places as "that awful negro", and that's seen as sort-of fine. So I don't care what y'all say about The Adventures of Pluto Nash, The Nutty Professor or Mel B – Eddie Murphy, for me, is The Man. Bill Murray is a god, obviously, but, if we're all honest here, his comedic repertoire is pretty much limited to the following.

1. Being the dryly cynical wiseacre;

2. Being the chaotic mess;

3. Being the dryly cynical chaotic mess.

Murphy, on the other hand, while being a worse dramatic actor than Murray, is far more varied as a comedian and can do pretty much anything when he puts the effort in. This is demonstrable not just in the variety of leading comedy roles he has played (he should have got at least an Oscar nomination for his performance in 1999's Bowfinger), but also in the little character sketches from his stand-up that he became so fond of tricking out in his films.

Probably the most amazing example of these is from 1988's Coming to America, in which he is unrecognisable as a chatty barber and an elderly white Jewish man (seeing as Murphy endured Aykroyd blacking up, it seems fair enough that he a few years later would then white up.)

But there's a hint of that in Trading Places, when Billy Ray pretends to be an African exchange student on the train and, earlier, pretends to be a blind and parapalegic war veteran ("I was with the Green Berets, I was special Agent Orange"), only then to be exposed as a phoney by the police who pick him up off the ground: "I can see! I have legs! Praise Jesus!" he cries, and his little grimace as he turns away from the police and towards the audience sums up the tone of the film: it winks just enough at the camera.

There are plenty of great Murray moments in Trading Places: when he pretends to be a kung-fu master in prison, when he's nearly strangled by Louis, when he accidentally nearly swallows a joint, when he sings in the jacuzzi ("They're very musical people, aren't they?" grins Ralph Bellamy). To its credit, Trading Places makes some notable efforts to undercut racism, particularly through Don Ameche's racist character, Mortimer. This, though, makes the blacking-up scene even weirder.

But I think my favourite Murphy moment is the little gesture he makes right at the end, pretending to wipe champagne from his mouth. It's classic Murphy: cocky, knowing and hilarious. He also clearly appreciated how fantastic Trading Places was because he and the director, John Landis, paid homage to it in Coming to America, which they also worked on together, by having the Duke brothers (Bellamy and Don Ameche) make a cameo in it. Murphy is known for many things, but graciousness is not one of them. I like that he was gracious to this film.

But Aykroyd should not be underrated here, and it is to his too rarely given credit that he is more than able to maintain the audience's attention even while sharing the screen with Murphy, a consummate scene-stealer (as he was the next year in Ghostbusters with Bill Murray, another attention-hog par excellence.)

He is at his funniest at his snobbiest, whether it's talking in baffling posh slang with his rich girlfriend ("OK with me, sugarpuff. Darn nice, too") or trying to pawn his watch downtown to Bo Diddley ("It tells time simultaneously in Monte Carlo, Beverly Hills, London, Paris and Gstaaaaaad"), although his drunk Santa routine has become a classic American scene, the dark side to It's a Wonderful Life. Always a sentimentalist, Aykroyd got a part in the film for James Belushi, the younger brother of his late best friend John Belushi, and it's not hard to imagine that Aykroyd envisaged a parallel world in which the elder Belushi was his co-star in this movie.

Of the rest of the cast, the best, of course, are the peerless Denholm Elliott as the wise butler ("Eggnog?") and Don Ameche, so delightfully nasty as Mortimer Duke (a million miles from what that charming Ameche was reportedly truly like.) But I think what I find so endearing about Trading Places is how it is like a sweet subversion of so many 80s films. Like many movies of the era, it is fascinated with the stock market and Wall Street (Working Girl, Wall Street, The Secret of My Success, etc etc.) Unlike those, it takes this interest to an extreme by making an entire comedy about the nerdy commodities market, which must not have been an easy sell as a comedy (I still need Michael Lewis to explain to me how exactly Lewis and Billy Ray tricked the Duke brothers at the end.)

Also unlike those films, and pretty much 90% of 80s comedies, this one is not set in New York – it's set, for no obvious reason, in Philadelphia. For some reason, I find this adorable, especially because it doesn't really make any sense and requires the characters to schlep around the country on trains to sell stocks and short the market. But just as Trading Places seems initially like a typical high-concept 80s comedy, only to turn out to be far funnier and smarter than that, so it takes the conventions of 80s comedies and tweaks them just a tad. (Like most of its contemporary films, though, Trading Places does, ultimately, celebrate wealth. Sure, the film might dabble a little in subversion but, come on, this was the 80s.)

It's true, there are plenty of things in the film that don't quite make sense, such as why Coleman is the butler for Louis yet in the pay of the Dukes. Or how Billy Ray changes in the space of six hours from a homeless scam artist to a houseproud prude. But come on, this is a Dan Aykroyd comedy – if you want realism, go find Ken Loach. Yet it's precisely because it's an Aykroyd comedy that the whole blacking-up scenes jars so woefully.

But then Murphy comes back onscreen and, well, I'm sorry to say that the beat is right so I keep dancing.