I understand this ask is satirical, with the goal of mimicking hard-right ideology.  Quite frankly, I’m not sure what the point even is, since for Libfas, it was probably an attempt to bait him into saying something that would “reveal” his “inner Nazi” or something along those lines.  

But not everyone with concerns about immigration truly has a secret inner Nazi with an opinion like your satirical one.  Leftists are just not that great at understanding right-wing motivations, statistically, from what I’ve read.

But let’s assume we take it seriously for one moment.  Just, you know, hypothetically.

Is there any way in which extermination is preferable to separatism?

Because not only does extermination require political will, it requires somewhere between one to three orders of magnitude more political will than separatism, control over the state apparatus, and conditions that, in the West, would only exist in a time of lawless violence and disorder on levels of Weimar Germany (which we aren’t at - note the insufficient challenge to the state’s military power).

And then, once extermination is attempted, because for such a nation to exist (at our technology level) for whites, it must exist in areas that are currently majority white, the full force of the political will of the liberal countries will crash against it, likely resulting in a much larger and better-armed invasion.

Separatism, however, won’t necessarily generate an invasion, and may have trouble rousing even a sufficiently crushing response in economic sanctions.

It would muster almost no response in sanctions if your ethnic separatist population was any color other than white.  However, supposing you really did believe this, that becomes a method to corrode your opposition’s political will - just repeatedly pointing out their hypocrisy on this matter.

So even if one were an extremely racist hardcore reactionary, it just doesn’t make much sense to choose extermination instead.

That doesn’t exclude people from holding such ideas, or even acting on them - after all, destroying the Twin Towers was never going to make America quit meddling in the Middle East.