By Eugene Robinson

WASHINGTON -- The erratic Trump administration has had just one consistent policy principle, one guiding North Star: punitive and often sadistic treatment of nonwhite immigrants.

President Trump's claim that he supports legal immigration, as opposed to the undocumented "invasion" he rails against, turns out to be -- big surprise -- a lie. On Monday, the administration proved its antagonism toward those who "stand in line" and "come in the right way" by issuing a new rule forcing many legal immigrants to make an impossible choice: accept needed government benefits to which they are fully entitled, or preserve their chances of obtaining permanent residence.

Say you're an immigrant from Mexico who came here legally to join family members who are already permanent residents or citizens. Say you're working a full-time minimum wage job, plus odd jobs nights and weekends. You are a productive member of society. You are paying payroll taxes, sales taxes, vehicle registration fees and other government levies. Still, as hard as you work, you can't make ends meet.

You may be legally entitled to health care through Medicaid. You may be entitled to food assistance through the SNAP program, formerly known as food stamps. You may be entitled to housing assistance. But according to the new Trump administration rule -- set to take effect in two months -- if you use any of these programs, you might forfeit the opportunity to ever obtain a green card making you a permanent resident. That means you also forfeit the chance of ever becoming a citizen.

Long advocated by White House adviser Stephen Miller, the Torquemada of the immigration inquisition, the new policy is a major step in Trump's crusade to Make America White Again. If it survives court challenges, the new rule could dramatically reduce legal -- I repeat, legal -- immigration from low-income countries. Not coincidentally, I am sure, this means fewer black and brown people would be granted resident status.

Trump's message to the world: Keep your tired, your poor, your huddled masses yearning to breathe free. As he memorably and disgracefully put it: "Our Country is FULL!"

This is part of a well-established pattern. Trump often uses immigrants as scapegoats, encouraging his supporters to blame them for any and all problems they face. But beneath the cynical posturing there appears to be genuine animus.

Does the president hate all immigrants? He did once allegedly muse about wanting more newcomers from Norway. But those who are not white are treated, by this administration, as if they were not fully human.

How else to characterize a policy of cruelly separating children from their asylum-seeking parents at the border? Of keeping children in cages and denying them toothbrushes or soap? Of cramming adults into overcrowded lockups when their only crime was to lawfully seek refuge from violence and persecution?

Last week, U.S. Immigrations and Customs Enforcement staged what was apparently the biggest one-day immigration raid in modern American history. Approximately 680 men and women classified as "removable aliens" were arrested at seven work sites in Mississippi. Taken from their job sites, many left young children waiting in vain, and in anguish, for their parents to pick them up from school or daycare.

ICE has limited resources -- certainly nowhere near enough to go after all of the estimated 11 million unauthorized immigrants in the United States. The only policy that makes sense is to prioritize the capture and removal of those who pose a genuine danger, such as MS-13 gang members. But that's not who you find punching a clock for minimum wage at a chicken plant in Mississippi. Instead, you find hard-working people trying to put food on the table for their families.

The raid was a demonstration, a warning, a show of force. If the administration were serious it would have gone after the employers, who were not immediately hit with charges or sanctions -- and are already looking for replacement workers. The message to undocumented migrants was: You are weak. We can hurt you whenever we want.

Sensible immigration reform would provide the law-abiding undocumented with a pathway to legal status and citizenship. But the Republican Party blocks action because it is terrified that these immigrants would eventually become Democrats. I wonder why.

I'm betting that not a single unemployed steel worker or laid-off coal miner moves to Mississippi to take those jobs plucking poultry. Trump's immigration policy isn't a matter of economics. Nor is it a matter of principle or fairness.

Cruelty isn't a sideshow in the way Trump deals with nonwhite immigrants. It's the main event.

Eugene Robinson's email address is eugenerobinson@washpost.com.

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