Such an issue as “I always decide for myself” versus “I go by the opinions of others” is extremely wide. If two characters started discussing it out of a clear sky, that would be sheer propaganda. But in the above scene, the two men are stating an abstract issue as it applies to their own problems and to the concrete situation before the reader’s eyes. The abstract discussion is natural in the context, and, therefore, almost unnoticeable.

This is the only way to state abstract principles in fiction. If the concrete illustration is given in the problems and actions of the story, you can afford to have a character state a wide principle. If, however, the action does not support it, that wide principle will stick out like a propaganda poster.

How much philosophy you can present without turning into a propagandist, as opposed to a proper fiction writer, depends on how much of an event the philosophy is covering. In the above scene, it would have been too early for the two boys to make more of a statement than they did, even though the issue stated is independence versus second-handedness, which is the theme of the whole book. Given what is specifically concretized in the scene, one exchange of lines is enough abstract philosophy.