Very true. Now extend the idea to areas within a city... Large ethnic communities form ghettos where they try and recreate their own culture and if allowed, create informal judicial systems... This is particularly visible in London, try walking out (if you dare) in Tooting, Croydon, Streatham and Brixton in the evening. Its not evident that your are in the UK at all.
The real issue is the reluctance to integrate, and for minority communities to realise that integration does not mean losing ones cultural identity.
bystander