why did the west commit to multiculturalism?

[Beskar]

The KKK wannabes 'round these parts consider everything short of "back to Africa" to be that, you know.
Pray tell what would be your particular criteria for "well-managed immigration"?

That would be a new one, I am being association with the Klu Klux Klan. As for your question, if you read my earlier posts, you would clearly see my criteria.

In short:
If everyone crams onto an island, it is pretty evident that very quickly, this island will not be able to support the population on it. In my example of Britain, Britain cannot support it's population without very heavy reliance on imports, it is simply too crowded. This is where population control comes in as the population of Britain needs to decrease, there needs to be more emigration from the Isles to elsewhere and this number needs to be greater than the influx. On the otherhand, there are other nations (Such as Poland) which require more (and want more) migration so they are able to have better use of the land and for industry.

Thus, waton immigration on the isles is a pretty moronic policy as Britain is no where near self-sufficient and this is decreasing rapidly with the decline of agriculture and industry. While a global trade policy you do not have to be able to be fully sufficient, however, you need your exports to be greater than your imports for viable economic growth and sustainability, which Germany is a very good example of.