In the recently leaked remix of Rihanna's Birthday Cake - a song lurid enough to make Prince blush - Chris Brown, her former boyfriend, the man who turned her face into a bloodied mess while threatening to kill her, sings lyrics so explicit they make for deeply uncomfortable listening.

The song is a provocative ode to a delicate part of the female anatomy and yet another in Rihanna's canon that purports to fly the flag of female emancipation in the bedroom but scratch the highly sexualised surface and something far more sinister begins to emerge.

If Rihanna is serious about having a lover respect her body and pleasure it accordingly as Birthday Cake's lyrics suggest, then why is the man who bit and beat her sharing vocal duties? For all the controversy, Birthday Cake sounds just like any other pop song dipped in pornography: built for shock value rather than listening pleasure. How better to get it to stand out from the din then by roping in the one male singer on the planet no right thinking individual would consider appropriate in a million years.

Rihanna has excelled as an agent provocateur and her material has grown ever more hedonistic and hyper-sexualised. She has released a staggering six albums in six years and in the rush to sell, sell, sell, she has thrown taboos about like confetti but recording two tracks with her abuser is beyond anything that has come before.

Despite his crime, Brown has a large, devoted female fan base; he still sells records by the bucket load and was awarded a Grammy last week. Clearly, the music industry is a very forgiving place, providing you keep the cash rolling in as Brown has done. Unfortunately, no award or amount of adulation can erase the horror of his actions, actions he still doesn't seem to grasp as completely abhorrent as his now infamous post Grammy tweet illustrates:

"HATE ALL YOU WANT BECUZ I GOT A GRAMMY Now! That's the ultimate FUCK OFF!"

Humble and chastened, young Mr Brown is most certainly not.

If the public take issue with Brown's continued success, what exactly is Rihanna - one of the biggest pop stars on the planet in her own right - hoping to achieve by making music with him? "Hey folks, I'm over it. Can we all move on please?" or "...with yet another new album on the market in the middle of a recession, I'm going to need to crank up the publicity machine tenfold - now, how can I do that in a jiffy? Sing an inappropriate song with the man who bashed me about? Bingo!"

Since the demise of her relationship with Brown, many of Rihanna's songs and videos have been thinly veiled homages to their time together. What her feelings are toward Brown and whether they will reunite romantically remains to be seen. What is clear is that neither they nor their management are particularly troubled by their turbulent history, in fact, they see fit to exploit it.

For two people who are clearly bad for each other not to have the common sense to leave well enough alone is tragic; using their doomed, abusive relationship as a marketing gimmick is a whole other level of wrong. No project featuring Rihanna and Brown can ever escape the lasting horror of her face in that photograph, battered and broken almost beyond recognition. In choosing to work together, they choose to remind us of it.

Rihanna once said she didn't want to be remembered solely for her disastrous relationship with Brown, which makes their duet all the more sickening and bizarrely misguided. Expecting pop stars to be moral guardians is often wishful thinking but in taking Brown to court and rebuilding her life, Rihanna became a hero to many young women, a fact she seemed to embrace. What would she say to them now? And for her fans that gained strength and took heart from her triumph, what explanation could ever be good enough?

Follow Mary McGill on Twitter: www.twitter.com/missmarymcgill