So -- the Berlin Wall, when built and staffed by East Germans, was a symbol of totalitarian dictatorship.
But suppose it had been built and staffed by West Germans. Would its moral nature suddenly change?
If so, it's curious that the morality of shooting would-be refugees changes with the color of the shooter's uniform.
Immigration is an issue that deeply divides libertarians. Although I suspect the majority of libertarians are open borders advocates, a significant minority favor strictly limited immigration. They fear that a horde of stupid, socialist immigrants will, among other things, overwhelm our water supply, clog our roads, steal our stuff, and vote themselves ever increasing amounts of welfare.
Pro-immigrant libertarians, on the other hand, emphasize the costs of preventing people from fleeing socialist hellholes, and finding work where they can best fulfill their highest potential. They also oppose immigration restrictions as unethical infringements on the right of association and the right to private property.
How could these differences be resolved, in principle? Some of the differences result from fundamaental differences in values. For example, someone who highly values woodlands is not going to be happy with Hong Kong population densities. Such valuations are aesthetic judgments that are unreconciliable via evidence and rationality. The best that can be achieved is to set up society in such a way that there are variety of environments, each suited to different tastes.
However, many differences regarding economic growth, crime, and effects on politics could theoretically be resolved. If economists were gods, for example, they could establish multiple universes, each differing initially only in the U.S. border policy. By comparing the outcomes in each of these alternate universes, the effects of different border policies could be measured and compared.
Unfortunately, economists are not gods.
However, what if we ran different border experiments at a smaller scale?
If the anti-immigrantion advocates are right, we should see benefits to limiting immigration at smaller scales. After all, if it's bad for a an illegal Mexican to enter my country, then isn't it also bad to allow a illegal Mexican to enter my state? Or my hometown?
So my suggestion is this: set up a dozen or so 10 x 10 mile plots in the Texas desert along the Mexican border. Each plot would be subject to the same laws as the rest of Texas, with one exception -- each plot would have a different border law. So one plot would allow anyone in the world to move and buy land there. Another plot would allow no one except existing Americans to buy land. Another plot would only allow those who passed an IQ test to enter. And so on.
Exit from each plot would be governed by existing U.S. law. If you're an U.S. citizen or green card holder you can pass freely. Otherwise, you would be treated as an immigrant from your country of origin, just as you would at any other border crossing.
To prevent illegals from crossing into the rest of the U.S., each plot would be surrounded on all four sides by a secure wall. This itself would be a valuable test -- if the U.S. border control can't contain a few 10 x 10 mile plots, they'll certainly be unable to prevent immigrants from crossing a continent wide barrier.
The health of the each of these plots could be measured. What's the lifespan? GDP? Disease rates? Population density? Crime rates? Partisans, at the outset, could wager on the future of each plot.
Presumably, over time, it would become clearer which border policy resulted in a healthier, wealthier society.
Moreover, if a particular border policy proved successful, the size of the plot could be expanded gradually, perhaps growing large enough to encompass the entire country. Thus, better border policies could be implemented, without the risk and disruption from switching abruptly to a new and unproven border policy.