Why do Liberals, Pro Multiculturalists & some ethnic minorities deny That British/English exists?

I don't believe anything you're saying. You go on about racists, but, from this question at least, I suspect that you're really the racist one. I bet you get offended when other people assert their own culture, and take that as an affront to British culture. Which is nonsense, since a British citizen is a British citzen, regardless of where they came from.