Answer:
Simon is frightened because he still sees it as murder. The other boys try to repress the events.
Step-by-step explanation:
Ralph feels guilty and a sense of dread about the death of Simon, whereas many of the other boys like Piggy try to rationalize it away by saying it was an accident. For Ralph, it was clearly still murder and he seems to be the only remaining boy with his moral compass still intact on the island. The others have lost at least some of their sense of right or wrong and they have pushed the idea that Simon's death was murder out of their minds as Jack callously seems to do, or they repress it like Piggy, calling it something other than murder or somehow blaming the victim.