Continuity mistake: When Vorenus ask Eranus where his children are, Vorenus raises both his arms. When it cuts, they are down.
Factual error: Cicero's secretary, Tiro, is seen throughout the series wearing a plaque around his neck marking him as a slave, and here Cicero tells him, "You've been freed in my will". However, Tiro was freed in 53 BC, several years before the events depicted in the series.
Answer: Its Pullo's nature to resent people of higher standing than him. His jealousy of Vorenus in later episodes, which in part leads to their falling out, is proof of that. From Pullo's point of view, Vorenus just got better breaks to get where he is in the army and so, isn't really his superior. That, plus his natural arrogance is explantion enough for his behaviour in spite of the fact that he broke the rules and was being fairly punished.
roboc