William Golding experienced first hand the atrocities of World War II, and this experience left him cynical about man's goodness.
In the novel, as soon as the boys are removed from civilization, they try to preserve society. However, their decorum and civility doesn't last long, and the boys turn savage. Their descent into savagery is best shown threw their appearance and their conduct toward the pigs and beast. After their civility is no longer redeemable, they become so lost that they murder Simon and then Piggy.
At the beginning of the novel, the conch symbolizes order and power. When the conch shell breaks and Ralph realizes it didn't hold any power anymore anyway, it is a symbol of how the boys have completely strayed from democracy and organized leadership. The double-ended spears are a symbol of savagery and animalistic behavior.
With Roger and Jack at the forefront, readers can see that these boys are evil. However, Golding does not excuse any of the boys besides Simon. Ralph, Samneric and even Piggy are all at fault for losing themselves to their animal instincts. Therefore, Golding's message is that humans are inherently evil. Without society's rules and expectations, people descend into animalistic behaviors and turn to survival mode. There is no compassion or reasonability at the end of the novel.