*I* think he did. Even without Pippin blowing their cover, Frodo did not really seem to have much clue as to just how far behind the Shire was...and that Bree was on the edge of the frontier...and the fact that he had the Ring lose showed that Frodo was not exactly taking his guardianship of the Ring all that seriously as well. Pippin can be forgiven for his youth and ignorance. Frodo, however, needed to be shaken into reality, because Aragorn knew that Frodo knew EXACTLY what he was dealing with and was not taking the necessary precautions. I think the roughing up was necessary to let ALL the hobbits know this was not a stroll through the countryside ANY MORE.