This is a good question. Let me set the stage for you. We see the tribune of the plebs, Flavius and Murellus in the streets with a bunch of common citizens. It is before the triumph of Caesar.
These tribunes basically tell people to stop loitering and get back to work. When a cobbler states that he is taking a break from work to see the military triumph of Caesar (one of the greatest glories a Roman commander can achieve), Murullus states that the triumph of Caesar is nothing great, because no foreign enemy was vanquished. If you know Roman history, Caesar defeated Pompey, another Roman general in a civil war.
Here is a quote that shows this:
"What conquest brings he home? / What tributaries follow him [Caesar] to Rome / To grace in captive bonds his chariot wheels?"
In a word, Murullus is making little of this military work of Caesar. In light of all this, we can say that the tribunes are pushing the commoners away and even reprimanding them, because they do not like Caesar and what he stands for, the potential end of the Republic.