OEV, you know that I agree with you on the issue of immigration/race, but are you really implying that ethnic diversity keeps all the problems you list in check? Because that's the impression I get. And it's kind of silly, to be frank.
Anyway, I'll answer.
A racially homogeneous white society is a (rather daft) dream for some that is impossible in practice (because whites are by no means homogeneous). If it actually happened, though, economically stuff would likely be more expensive, and there'd be far less foreign produce, and thus much less competition (which comes into higher prices).
In terms of society, there might be less religious diversity (but if we're fancifully speaking of a dreamy future, who's to say that a new religion won't spring up in the west?). There'd also likely be more widespread racism and xenophobia (due to no contact with other races).
I don't really understand why it's such a utopian vision for the far-right.