He also writes: "The entire human body, faced with a strong impact like being gored by a rhinocerous horn, will fail at its weakest point, not its strongest point."

If a rhino comes at Yud, he can use his mighty cranium, which is not his weakest spot, to defend his weak meat parts. Since the rhino horn only impacts his head and not his weak points, his body can not fail, and thus he lives.

Reminds me of Cyrano de Bergerac's Travel to the Sun, where the protagonist encounters a thin chain carrying a great load. Since all links of the chain were equally strong, it couldn't break as chains always break in there weakest link. De Bergerac had the excuse of writing his sci fi in the 17th century (he also features some pre-Newtonian physics), Yud lacks such an excuse.