Despina at 2013-08-19 20:22:42:
I can't find the screenplay anywhere, but I just watched Mud this wknd so this scene is fresh on my mind...
http://www.youtube.com/watch?v=RJmJXjd_HQM
Ellis had been rather subdued and trusting throughout the story until seeing the dissolution of his parents' marriage, having his own heart broken by a girl he loved and who he thought loved him back (or, at the very least, liked), and being the unwitting bearer of bad news on behalf of Mud to Juniper (Mud's 'love') when he finally breaks down as everything collapses around him. He's had it! He's hurt and frustrated... and rightfully so.
Seems a sort of right of passage as the jaded innocence of adolescence fades away.