A BOOK, “The Christian Examiner,” warns that “ill-clad and destitute” immigrants are “repulsive to our habits and our tastes.”A former mayor of New York City cautions that they bring disease, “wretchedness and want” to America. And Harper’s Weekly despairs that these immigrants are “steeped in ignorance” and account for a disproportionate share of criminals.

Boy, those foreigners were threatening . back in the mid-1800s when those statements were made about Irish immigrants.

Once again, the United States is split by vitriolic debates about how to handle immigrants, following President Obama’s executive action to shield millions of undocumented immigrants from deportation. To me, the outrage seems driven by three myths:Immigrants threaten our way of life. Many Americans see foreigners moving into their towns, see signs in Spanish, and fret about changes to the traditional fabric of society.

That’s an echo of the anxiety Theodore Roosevelt felt in 1918 when, referring to German and other non-Anglo European immigrants, he declared, “Every immigrant who comes here should be required within five years to learn English or leave the country.” That’s an echo of the “yellow peril” scares about Chinese and Japanese immigrants.

It’s true that undocumented immigrants may lower wages in some sectors, harming low-skilled native-born Americans who compete with them. One study suggests that a 10 percent increase in the size of a skill group lowers the wages of blacks in that group by 2.5 percent.

Yet just look around. Immigration has hugely enriched our country. For starters, unless you are a full-blooded American Indian, we have you.

Nations, like carpets, benefit from multiple kinds of threads, and Tony Blair, the former British prime minister, was right: “It is a good rule of thumb to ask of a country: Are people trying to get into it or out of it?”Immigrants today are different because they’re illegals. They’re parasites.

Look, people aren’t legal or illegal, behaviors are. If an investment banker is convicted of insider trading, he doesn’t become an illegal. So let’s refer not to “illegal immigrants” but to “undocumented immigrants.”They have contributed $100 billion to Social Security over a decade without any intention of collecting benefits, thus shoring up the system, according to Stephen C. Goss, the chief actuary for the Social Security Administration.

At the state and local level, households headed by unauthorized immigrants paid another $11 billion in taxes in 2010 alone.

If these migrants are given work permits and brought into the system, they will contribute $45 billion over five years in payroll taxes to the United States economy, according to the Center for American Progress.

Parasites? No, they’re assets.

Immigration reform is an unconstitutional power grab by a dictator.

Senator Ted Cruz compared Obama’s executive action to the Catiline conspirators seeking to overthrow the Roman Republic. House Speaker John Boehner suggested that it was the action of an “emperor.”Look, I’ve reported in many dictatorships (and been detained in some of them). And Obama is no dictator.

It’s difficult for me to judge the legality of Obama’s executive action, because I’m not an expert on legal issues like prosecutorial discretion. But neither are critics furious at Obama. We have a broken, byzantine immigration system . anybody who deals with it is staggered by the chaos . because politicians are too craven to reform it. At least Obama is attempting to modernize it.

Yes, it’s troubling that Obama previously argued he didn’t have this authority. Yes, his executive action is on a huge scale . but it is not entirely new. Obama’s action affects 45 percent of undocumented immigrants, compared to the 40 percent affected by President George H.W. Bush’s in 1990. Let’s leave the legal dispute for the experts to resolve.

I see a different hypocrisy in Obama’s action. He spoke eloquently Thursday evening about the need to treat migrants humanely . and yet this is the “deporter in chief” who has deported more immigrants than any of his predecessors. We as taxpayers have spent vast sums breaking up families and incarcerating honest men and women who just want to work. By a 2011 estimate, more than 5,000 children who are United States citizens are with foster families because their parents have been detained or deported.

We need empathy, and humility. My father, a refugee from Eastern Europe, was preparing a fraudulent marriage to an American citizen as a route to this country when he was sponsored, making fraud unnecessary. My wife’s grandfather bought papers from another Chinese villager to be able to come to the United States.

So remember: What most defines the 11 million undocumented immigrants in America is not illegality but undaunted courage and ambition for a better life. What separates their families from most of ours is simply the passage of time . and the lottery of birth.