How do the nobles in Julius Caesar speak of the citizens in Rome?
In this play, the citizens in Rome are mostly dealt with as a mob. They are lumped together and referred to as the "citizens", as if they are of one mind. In the first Act of the play, there is a short interaction between some of these citizens and the nobles Flavius, Marcellus, and some citizens on the street. Shakespeare gives proper names to the nobles, but the citizens are known only by their occupation, "Carpenter" and "Cobbler." In addition, in the first line, Flavius calls them "idle creatures." Further on, Marcellus uses the term "knave" and "saucy fellow" in reference to the Cobbler.
Shakespeare is clearly drawing a disntinction between the two classes in this first scene, and he carries that distinction throughout. In Act III, there are again some speaking lines for the general population. However, they are given the names "First" and "Second Citizen" only. These citizens demand to hear explanations of the Caesar's murder, and claim they will carefully consider the speeches. But Antony proves clearly how easily they can be manipulated. He lies to Brutus and carefully plays the audience to make them forget all that Brutus says, showing his feeling of superiority to these plebians.
Brutus himself is the only noble that shows respect for his lower class countrymen, considering what is best for them and trying to honestly explain his motives. However, his assumption that he does know what is best further underscores that sense of superiority that the other nobles show.
The answer to your question depends upon which nobles you are discussing. In regards to Caesar and Antony, they view and speak of the Roman citizens as pawns and as those with lesser intelligence. While the citizens believe that Caesar loves them (he engenders this belief by generously sharing the spoils of his victories and by leaving them each a stipend in his will), he strategically feeds into their adoration to advance his own agenda (ultimate power). Antony, upon Caesar's death, treats the citizens in the same manner. He stirs them into a frenzy with his funeral speech, and then in Act 4 implies that they are blind enough to follow the triumvirate's every whim.
In contrast, Brutus--another noble--seems to care sincerely for the citizens and through his speech at Caesar's funeral speaks to them as intelligent individuals, expecting them to understand the nobility behind his actions. Similarly, when he and the other conspirators are plotting, Brutus always keeps in mind what the citizens' response will be to their actions (he nixes Antony's assassination because he does not want the people to think of them as butchers).