In what follows, I'll try to show that they are right. Immigration of elements hostile to American values does indeed pose a grave threat. But, if we are libertarians, don't we have to defend "open borders"? I will argue that we don't.

One of the most obvious reasons mass immigration is a problem is its immense cost—hundreds of billions of dollars. A post from November 2023 that appeared on Judicial Watch explains:

"Mass illegal immigration resulting from the Biden administration's open border policies is costing American taxpayers hundreds of billions of dollars to provide an unprecedented number of migrants with medical treatment, housing, education, and other welfare services, not to mention law enforcement. A new congressional report that includes federal and state figures reveals the shocking price of supporting an estimated 16.8 to 29 million illegal aliens currently living in the United States. The "net cost of illegal immigration is greater than the annual gross domestic product (GDP) of 15 different states," according to the lengthy report, published this week by the House Committee on Homeland Security. "Illegal immigration costs every American taxpayer a net average of $956—or $1,156 before the taxes paid by illegal aliens are factored in."

Healthcare is among the biggest expenses with Medicaid costs for "emergency services for undocumented aliens" exceeding $12.4 billion in the last two years, according to figures provided to committee members by the Centers for Medicare and Medicaid Services. In fiscal year 2022, which ended in September, improper Medicaid payouts across the U.S. totaled more than $80 billion with around $8 billion going to illegal aliens. In New York City hospitals recorded about 30,000 visits by illegal immigrants in the past year along with approximately 300 births. A Yuma County, Arizona lawmaker recently testified before Congress that the maternity ward and emergency room at Yuma Regional Medical Center has incurred over $26 million in uncompensated costs for illegal immigrants.