That goes for people on all sides.
The world is a truly global place now, maintaining some sepia tinted idea of cultural mores from half a century ago is simply pointless. Not only does that person lose out, society as a whole does.
I still don't know what the alternative to multiculturalism is, especially given we have such a multitude of cultures anyway.
I might have got the whole Britain thing wrong, god knows I often do, but isn't it literally a country built on a multitude of cultures anyway?