I think the OP revealed the extent of his problem by admitting that "I have yet to meet any of them joining to fight for Britain", when there are many in the police, security services, and yes, even the armed forces.
His next line will be "oh, yes, but I don't mean black people/the Muslim chap I know/the British Indian RAF pilot" (delete as appropriate) - the mark of a true racist, who generalises, but makes exceptions for the few he does know.
And yes, I do know of British ethnic minorities in the armed forces, but perhaps the reason they are not in the armed forces straight of the boat is that it might, in itself, be an inappropriate security risk...! Damned if you do...damned if you don't.