There is a higher proportion of African/Carribean men in prison for sexual attacks on girls than Asians, and the statistics for identifying the race of their victims are not available. The stats vary to reflect different parts of the country e.g. in London there has been heavy sex trafficking of eastern European girls into fictitious 'nanny' jobs for British families, but they have been threatened and virtually imprisoned by sex rings of men from a variety of races. Police are challenged in trying to profile both perpetrators and victims as recruitment is done on the internet, and girls are either smuggled over or arrive as visitors, then disappear.
In metropolitan areas there will always be a racial mix of criminals, and it's easy to look for the racist view of offences, when the issue is criminality and access to potential victims. If someone has the urge to commit a sexual crime, they need the opportunity and means to do it, a chance to remove the potential victim from their protectors, whether that be parents or friends, a way of overcoming that victim's resistence, by threat, bribery or grooming, and a way of keeping them quiet afterwards. Asian men are not generally socialised into committing sexual crimes - these are men who would be criminals if they lived in any country, and their choice of victim would relate to who they could prey on, even in Pakistan or other south Asian countries.
Criminals are criminals - profiles of their offending will often show that sex attackers are generally criminal, and will have other convictions for theft, stealing cars, driving whilst drunk or without insurance, possessing weapons and so on. These particular men also deal drugs and will pimp girls and women, take their money, sell them the drugs they introduced them to, and sell their services to other men. That isn't in any way related to Asian cultures, which are many and varied. They didn't learn this at their parents' knee, nor in the mosque. We criticise those strict Asian parents who reject their children for making relationships from other cultures, criticise them for not sharing information with the police, criticise them for protecting their own, but if you wandered into the deprived streets of central Manchester where communities of predominantly white, poor people live, you would find something to criticise there, too. It isn't exclusive to Asian communities. If you want an example of communities protecting their own from the police, there's no better example than some of the districts on whcih the programme Shameless has been modelled. I only watched it a couple of times - it was too much like being at work!!