Even if we call this an illustration and a celebration of youthful rebellion, that doesn't mean that parts of the rebellion are not being satirized as well. Sammy fits a role that is part knight, part existentialist, and part rebel. He challenges authority for his own rebellious whims but also for the honor and approval of Queenie. This act of rebellion and romance is significant to Sammy, but in the context of other larger forms of rebellion and courageous acts of knights and so forth, there is a slight satire on Sammy's gesture. He is not rebelling against unforgivable social oppression nor is he slaying a dragon to save the maiden. He simply quits his grocery store job. So, this is a celebration of rebellion, but it certainly has an ironic or satiric component if we compare it to other, more grandiose notions of rebellion and romance. But such is the nature of learning how, why, and when to rebel. This is a learning epiphany more than a triumph of a seasoned rebel.
Lengel represents the "powers that be." In this case, Lengel (to Sammy) represents the establishment, the infrastructure, and the authority that he must challenge in order to complete his rebellious gesture. Sammy succeeds, even though this leaves him in a limbo state of having no job and no recognition by Queenie and her friends. It is a bit satiric that Lengel fulfills this role as the oppressive, reactionary generation of Sammy's parents' era. All he does is enforce his store policy of wearing clothes. He is not being terribly oppressive. So, Lengel is satirically morphed (from Sammy's perspective) into this stubborn authority figure that just doesn't get kids these days. Although Sammy and Lengel are satiric versions of rebel and authority, the story is nonetheless about a legitimate moment in a young man's life when he first tries out rebellion. It is a legitimate gesture because it will have consequences for him, and therein lies the courage.