I read a book a while ago called Sick Societies, by Robert Edgerton. It dispelled the myth of the 'noble savage' by illustrating many tribal societies which were both savage and ignoble.
Now we live in a country that has been pumped up by Al Grasby (a past politician) to the undefined and tendentious idea of 'multi-culturalism'. Undefined, because 'culture' is not defined.
Most people have a positive view of the 'decorative' aspect of culture: art, dress, cuisine, dance, etc. Decorative because these are innocuous observables, and we all love (mostly) variations in art, dress, cuisine, dance, etc. or at least, don't find them objectionable, and if so are able to avoid them.
On this basis, many support multi-culturalism, because it is not really multi-cultural, it is multi-racial with mixed entertainment.
Culture is initially hard to pin down, but I pin it down this way: it is the shared assumtions a group has about mutual rights, responsibilities and roles. This is the last place that 'multiple' works. For example, how does a society work where one group believes that the males of the extended family determine the choice of husband of the females, and feel obliged to murder any females that reject this, when most of the society believes that females are able to make their own choices and murder of them is criminal? Merely two different cultures at work...but now harmony; instead warfare!
Once cultures are so disparate, common behaviour mores cease to exist and society fractures.
On to the sermon of the day, on Colossians 3:9, where acceptance of disparate cultures was espoused. I don't think it was thought through. How does a culture that seeks to conform to Pauline ethics co-exist with those that reject them?
Paul knew the issue, because this was resolved IN CHRIST! Outside Christ, there is no resolution; the moral community, the spritual community does not exist and society thus remains fractured. But in Christ, we are brought together. This is the gospel, not some empty adulation of 'multi-culturalism.