I think that it's also perfectly possible to acquire misogynistic beliefs from 'western' cultures (just look at the Roosh thread).
Just as it's perfectly possible for tactics and techniques for street robbery and/or sexual aggression to be recombined and refactored across different criminal and/or counter-cultural milieus.
These suspects for these crimes have inevitably been exposed to all kinds of different influences, whether 'cultural', media reports and social media interactions or criminal 'apprentice' schemes and tradecraft, and it's not at all a given that they brought all of their misogynistic attitudes and robbery / sexual assault tactics with them and didn't get any of it here.
If anyone wants to seriously claim that it is something exclusively due to ethnicity (I'm pretty sure you weren't actually claiming that, but rather citing it as a likely influence) then I think that I'd like to see some compelling evidence.