When Ralph takes off his clothes, he is showing his independence and freedom from civilization and adults.
"You knew, didn't you? I'm part of you? Close, close, close! I'm the reason why it's no go? Why things are what they are?"
When Ralph first saw Jack and the other choir boys still in their robes, he compared them to a beast. This is ironic due to how bloodthirsty and savage-like Jack and his "hunters" become at the end of the novel.
*Wooshing rock noises*
*Screaming* *Water Splashes*
While Rodger is throwing the stones at Henry, Rodger is held back from hitting Henry due to Rodger being scared of punishment. Civilization holds him back.
"... Having a war or something?"
The pig's head on a stick tainted Simon's happy place, along with making the beast something to worship. The pig's head lastly showed how, without laws, barbaric civilization can be. (Well, lack of civilization can be)
Piggy's death was also the end of authority with the death of the conch as well. Rodger has also gotten over his fear of punishment due to him murdering Piggy with no chastisement.
Ralph is crying due to the end of childhood, the evil of man, and the loss of Piggy. This scene is also ironic due to the adult finding them and asking if a war has been going on sarcastically, because a war really has been going on.