Why is it ironic that Johnny throws sand in Percivals eyes?

In
chapter 4, Henry, Johnny, and Percival are playing peacefully by the water, building sandcastles
and minding their own business. As the boys are intensely focused on playing,and Maurice run out
of the forest and interrupt their game by destroying their sandcastles. As the biguns run away,
Percival begins to whimper after getting sand in his eye. Maurice experiences minor feelings of
guilt and remorse for getting sand in Percival's eye but only manages to mutter an apology as he
continues to run away. Following the incident, Percival's tears wash the sand from his eyes, and
he finishes whimpering. Once Percival composes himself, he continues to play.

As Percival is playing, Johnny proceeds to throw sand into the air, and Percival begins
crying again. Johnny recognizes that the sand makes Percival cry, which suggests that his
actions were intentional. Theis that one would assume Johnny desires to play with Percival and
would not purposefully make him cry. Before Johnny and Percival were interrupted by Maurice and
Roger, they were perfectly content playing together. Johnny's actions are ironic and indicate
that he is beginning to take pleasure in causing others pain. Considering Johnny's civil
upbringing, it is ironic that he would want to harm one of his playmates. Johnny's hostility
toward Percival underscores Golding's primary theme regarding mankind's inherently wicked
nature.