Greg Sargent at the Post spells it out about the white nationalist motivation.

This year Democrats repeatedly offered Trump deals with money for the wall in exchange for protecting the dreamers, and he rejected them all, because Trump also wanted deep cuts to legal immigration. After that, multiple immigration packages failed to pass the Senate. The one based on Trump’s framework — citizenship for 1.8 million dreamers traded for $25 billion in wall money and deep cuts to legal immigration — got the fewest votes, at 39, with 14 Republicans defecting.

The bottom line is that Trump will not accept anything that protects the dreamers unless it also contains deep cuts to legal immigration. But nothing like that can pass Congress, because it faces bipartisan opposition.

Trump’s tirade at Nielsen is a reminder that he is the real obstacle to any deal protecting the dreamers. It reminds us of Trump’s bottomless irrationality on this issue: Border crossings have been at historic lows, but #Foxlandia keeps telling him the border is overrun by invading dark hordes, which makes it true.

It’s the invading dark hordes. He hates them.

Indeed, it has become undeniable that Trump’s overriding goal on immigration is to reduce the number of immigrants in the United States to the greatest degree possible. As Eric Levitz notes, Trump moved to end temporary protected status for various groups with no credible rationale for doing so and even though U.S. diplomats have warned that it is dangerously bad policy. And as Trump’s “shithole countries” comment confirmed, his main driving impulse on immigration is white nationalism — rolling back the current racial and ethnic mix of the country at all costs — and this is shaping policy.

More white people! Fewer brown people! More yellow hair, less black hair.