The gangs didn't avoid prosecution because the police wanted to avoid being racist. Asian men are more likely to be stopped and searched and arrested for other offenses than white, so why do you think in this case they are worried about racism?
The girls weren't "negatively effected because of their colour" the research into these gangs shows that the amount of abuse within their own communities is of a similar level, just more likely to go unreported.
Even if they were negatively effected in this case because of their skin colour it doesn't mean that they don't benefit from white privilege!
Kate is not described as pushy or needing to know her place nor were other royals. In fact its been shown on here that for exactly the same actions Meghan receives negative press whilst Kate didn't, all with this undertone of MM needing to know her place.