The Ivy League MD/PhD I quoted was hurt that I distrusted his signature line; without identifying him (“No attribution, I am trying to get promoted here!”), I’ve googled him and he is, in fact, an authority. And he offered an interesting analogy to a nation’s need for border control:
If I may be permitted an analogy from my subspecialty, that of cell death. One of the most agreed upon and conclusive pieces of evidence that a cell is dead is that it no longer controls what comes into and out of it due to defects in its border, the plasma membrane. Such a cell gets eaten up by other cells.