A much, much simpler economic reason why, (say for example),
someone could not purchase a strip of land across Texas and prevent passage across
(as the show put it, suppose the KKK only wanted to let "whites" through).
Can you imagine the cost of the last 50 miles of free-passage land between countries?The ability to pass between Mexico & the US is so highly valued in raw dollars even now,
unscrupulus people make massive profits with fake documents and vans.
As the difficulty of moving people increases the more it costs to move any one of them.
Per your request on the show, I believe this is simple enough for a 5th grader

The laws of Economics are as valid and as real any any law of physics.
I mean this quite literally. The most well-understood economic laws are
those in idealized situations: millions of people, all acting (too) perfectly reasonably.
This is no different than the fact that Newton's Laws only hold for moles (zillions) of atoms, all acting like little marbles.
Ian, you should
really read
The Economist.
No, I don't get a commission, it's just the easiest way to educate you.
By your own (rather concerted) effort, your your opinions are broadcast widely. As such, they may just have an effect.
So please, if you won't do this it for me, do it for my children
