No idea where you are, but I did a quick search and in Britain a recent immigration poll found Britain to be moderately high in anti-immigration,

44% want it reduced. How many of those asked were native white british people?

Nobody wants to eradicate you, how about you marry and have children?

Even if I had 100 kids, the result would be the same.

Most of us accept the fact that race has been twisted and pushed as an issue specifically to divide workers, a point I feel like you may have missed?

No, I see it as yet another argument as to why homogeneity is better. In fact that's one of the reasons why they're pushing immigration.

and I do in fact think black lives matter, although I disagree with the organization itself

Well, then we seem to agree on that point.

This is trumped by people already living/being born there having a right to exist

No it's not. It is not a human right for turks to settle in France or for Somalis to settle in Sweden.

Why does the existence of a non-white in your country threaten self-determination?

Because we live in democracies.

Why do you believe countries are defined more by race, rather than culture, industry, environment, etc.?

It's one aspect. I personally don't care about race. But I'm forced to care because someone has the intention to destroy and genocide my own race.

Go found an ethnostate somewhere else where the majority agree?

No, thanks. We already have ethnostates in all of Europe. I don't need to found anything, because my forefathers already did. I just need to defend whats ours.

How does this work?

It's a strategy that's been used throughout history.