Cops with Molon Labe tatoos and enforcing laws at controversy with classical Constitutional interpretation are poster children for Stockholm Syndrome.
I would suggest that this includes the modern anti-free-migration stance.
The problem that most pro immigration control advocates have with free movement of people tends to be the impact on the welfare state. The next biggest complaint is the impact upon wages for unskilled and low skilled labor.
I've yet to encounter an immigration restriction advocate that could articulate any reason (actually based on immigration, not impact on welfare or labor supply/demand curves) why Ellis Island should have allowed a 98% blind admittance rate, but that current policies which come closer to a 98% rejection rate are appropriate.
It's a rare control advocate that can articulate concerns over crime, terrorism, or contagion of a deadly 3rd world disease. And they don't seem to care about the Ellis Island reference and its allowance for enormous organized crime utilization during Prohibition (which certainly rhymes strongly with Prohibition 2.0 against various illegal drugs, and our southern border).