Merrick had trained well as an acolyte at his temple, one of the most dire lessons being facing the unholy horrors that his calling might provoke him to face. He was taught to be brave and stalwart in the face of such evil, and how to counter it with his faith. The shambling horror before him was his first experience facing it, and he fought inwardly to resist the terror that was gripping at his muscle, trying to force his will over his body so as to sustain his companions.
Even still, the young idealist found his desperate reach for the symbol hanging around his neck was forestalled, as the true horror of their situation locked him muscles in place, preventing him from exhibiting his courage for the others to follow.