An example showing why Lord Of The Flies is pessimistic is the fact that World War 3 is happening and all of the kids are stranded from their parents instead of being optimistic and being dropped off at another safer country far away from the war. Instead of letting the kids reach their destinations he has them shot down in what seems to be a wonderful place slowly turning into hell.
The three deaths also show the evilness. One child burning to death in a wild fire , Simon being beaten to death by his fellow friends and Piggy who was crushed by a rock. Through out all of these killings most of the kids knew this was wrong but no one to stop them and discipline them . They all eventually lost their sense of life.
The only part of the novel where you feel that the kids fate may have made a turn for the better is the ending finally rescue. Or is it rescue? They might possibly be shot and killed on their way home , they might just be thrown into the mixi of a war , most of them will probably have to go through psychiatric treatment and will they have anyone to go home to? Who knows what will be left of their families and homes.
With all these grizzly details Golding must have had a pessimistic view to wars and he definitely showed that kids are not just little angels but have a much darker side.