To these people "brutal third world dictatorship" just means "punishing criminals". If you execute people for mugging or repeated illegal entry you're a third world dictatorship even if you have Maglevs, vast wealth, gun ownership and castle doctrine for real citizens.
You really think that you can just magically close the border. The only way to end all immigration to your country is by turning your country into a brutal third world dictatorship like Eritrea or North Korea.