By chapter four, life is relatively stable and predictable. In some ways, it is like a state. In this context, the younger boys (littluns) look up to the older boys. Older boys like Ralph and Simon are kind to the young ones. However, Jack and Roger are not very nice.
Roger begins to break the sand castle of the littluns for no good reason. Later he begins to throw rocks at them. He does not hit them, but this gesture is mean-spirited nevertheless.
Roger's behavior here begs for explanation. Why did he throw rocks and why did he not hit the younger boys?
Golding does not leave us to guess. He writes:
Here, invisible yet strong, was the taboo of the old life. Round the squatting child was the protection of parents and school and policemen and the law.
Golding's point is that Roger's understanding of past society curbed his depravity. Society functioned as a check. As the novel progresses, society breaks down. The new rule will be might makes right.
As for Golding's view of humanity, it is negative. Left alone, apart from society, man takes power into his own hands for ill. Roger's actions here, which seems harmless, are anything but.