While not the most profound scene, the misunderstanding of Cinna's true nature adds humour to the play, and highlights the aftermath of Caesar's death.
Mark Antony's speech at the Senate House ignited a passionate and bloodthirsty vengeance within the Plebeians. This vengeance is so intense that even when Cinna explains that he is a poet, the citizens choose to disregard the fact and instead "tear him for his bad verses!"
The passion of the people is also a representation of Mark Antony's rhetoric, which is plausible to also be called manipulation. He appeals to the emotions and the values of society to catalyse his own ascension. This leaves the conspirators to flee for their safety in fear of being tortured by the 'firebrands'.
While the impetus of the public's actions are fairly just, it can be argued that their excessive use of brutality, including attacking innocent citizens, removes some of the legitimacy behind their campaign.