"Marvel not that having been made acquainted with the young s..." — Herman Melville quote meaning

Marvel not that having been made acquainted with the young sailor's essential innocence (an irruption of heretic thought hard to suppress) the worthy man lifted not a finger to avert the doom of such a martyr to martial discipline. So to do would not only have been as idle as invoking the desert, but would also have been an audacious transgression of the bounds of his function, one as exactly prescribed to him by military law as that of the boatswain or any other naval officer. Bluntly put, a chaplain is the minister of the Prince of Peace serving in the host of the God of War -- Mars. As such, he is as incongruous as a musket would be on the altar at Christmas. Why then is he there? Because he indirectly subserves the purpose attested by the cannon; because too he lends the sanction of the religion of the meek to that which practically is the abrogation of everything but brute Force.