In chapter five, Ralph spends a great deal of time worried about how he can possibly maintain his leadership given his inability to think ahead of things and adapt to the changing situation. He knows that Jack has an advantage, but he cannot figure out how to take back that advantage. He notes that Piggy can think through things so well, but he cannot do the same.
So when he calls a meeting and tries to maintain order, the boys quickly tire of his rules and his urge for control, particularly when they are confronted with the alternative, which was Jack's idea that they simply have fun and hunt and stop worrying about trying to get rescued.
At one point, Piggy is trying to point out to the boys that following Jack's plan is a bad idea, but Jack butts in and says, "You shut up, you fat slug!" And Piggy tries to quiet him by pointing out that he doesn't have the conch, but with little success.