A multi-ethnic society cannot thrive if we encourage people to cling on their own. As my parents always told me, "We didn' t send you to Britain to be a Russian in Britain - we sent you there to become British"
The very notion of cultural relativisim defies all logic and empirical evidence, but that's the primary reason why you must adopt it. After all, logic, reason and evidence are all Western features, so you should hate them.