Look at it this way. When we or the Brits get enough of those working foreigners over here or there, they will pick up our habits along with our jobs. They will stop having kids, while we will all go on welfare.
In the 1960s and the 1970s, the United Kingdom imported tens of thousands of laborers from Bangladesh and Pakistan, to fill the manpower gaps in the textile mills of Northern England. Now their descendants number more than two million. And despite living in the United Kingdom for more than half a century, these people have shown no interest in assimilating to the British culture.
Diversity of thought is not bad at all.