When it comes to the fight on the beach between Daniel and Johnny I have always thought it was simply that, a fight between the two that started because Johnny was angry and looking to kick some butt and Daniel just happened to get in his way.
Although after reading the book a new possibility has crept up, the possibility that Daniel stepped into the argument between Ali and Johnny to deflect his anger away from her in an attempt to protect Ali.
Chapter 3, page 14
Suddenly, Ali's radio blared so loudly that everyone turned. They saw Johnny trying to yell over the sound and then watched as he turned off the radio.
"I don't want to talk," said Ali, defiantly. And she turned the radio back on. Johnny grabbed it from her and threw it into the sand near Daniel who went to pick it up.
"Don't touch it!" yelled Johnny. Daniel picked it up anyway.
"You deaf?" Johnny ripped the radio from Daniel's hands.
Daniel wasn't sure what was going on except that he could tell Johnny was about to explode. He hoped it wouldn't be at Ali.
"Come on, man," Daniel said in a voice he hoped would calm.
Johnny held out the radio to Daniel. "You want it?" he asked menacingly. Then, suddenly, he rammed the radio at Daniel, knocking him down.