The wording of this verse is fascinating. Lehi fears for Laman and Lemuel, should Nephi suffer again. Lehi does not fear that Nephi might suffer again. He does not fear that Laman and Lemuel might cause Nephi to suffer. Lehis focus is not on protecting Nephi, but rather on the effect that he can see that such continued persecution of Nephi would have on Laman and Lemuel.
Lehi attempts to reason with Laman and Lemuel by explaining (not doubt an explanation he had given many times before) that Nephi's ascendance was not due to a desire to gain power and authority (emotions Laman and Lemuel likely understood all too well) but rather a desire to seek the glory of God (an emotion that they likely did not understand at all).