If some people (of any race) have done something it isn't racist to say so, it's fact. If the reader concludes every person of that race does the same when it hasn't been said perhaps it's the reader at fault. If I said some white women were beating up an Asian man would you conclude all white women beat up Asian men?
Absolutely racism should be called out where it exists but not when it's based on the reader's assumptions. The abuse in Rochdale shows what happens when people are so frightened of being labelled racist they don't act when they should.
it's the context in how relevant it is to describe someone's race. If its used to visually recognise someone (like a police statement to be on the lookout) then that works, but to use it when describing someone's behaviour doesnt.
Rochdale had so many racist issues, the police ignoring in case they were accused of being racist, and the racist assumption by these men that white girls were trash. The gangs being Asian wasn't relevant as not all Asian men have this belief or behave in that way. The links the police found between the gangs, which they were afraid to act upon, were the culture of those types of gangs and not the race of those involved. That part can be tricky to separate though when they are all formed of the same race! Hence, you need more information of their activities to ensure you are not barking up the wrong tree.
I think it's good to have these conversations rather than getting angry as it's helps to educate.