Because Britain is our ethnic homeland.
Britain is nothing more than land on a map if it is not inhabited by the British people.
Considering how much Britain has f**ked up the rest of the world, it's hard to be too upset at the rest of the world returning the favor and screwing up Britain.
Past British governments did everything they could to wipe out the languages and cultures of Africa and the Indian sub-continent, why should Africans and Southern Asians show British culture and the English language any more consideration than they were given?
I kind of sympathise with what's going on in Britain, but it's hard not to connect it with past British policies. Maybe the British voting public should start making better choices than they have for the last 30 or so years.