Be hung with Caesar’s trophies. I’ll about the streets; / So do you too, where you perceive them thick.

And keep us all in servile fearfulness. (1.1) 

If we thin out the crowd of Caesar supporters, then we help lower Rome's enthusiasm for Caesar and his return.

Be hung with Caesar’s trophies. I’ll about the streets; / So do you too, where you perceive them thick.

These growing feathers plucked from Caesar’s wing / Will make him fly an ordinary pitch, / Who else would soar above the view of men

And keep us all in servile fearfulness. (1.1)

Fear - Flavius uses fear to motivate Marullus to help him thin out the crowd and remove the decorations from Caesar's statues. If they don't lessen people's love for Caesar, then they will live in fear of Caesar's growing power over all of Rome.

And will not palter? And what other oath / Than honesty to honesty engaged / That this shall be or we will fall for it? (2.1.135-139)

Brutus appeals to their status and credibility as honorable Romans. This is why they shouldn't have to swear an oath because they're Romans, and as Romans they have credibility and honor of doing what's right.

If that were true, it was a terrible fault,...He has brought many captives home to Rome,

Whose ransoms filled the government treasury.

Did this seem ambitious in Caesar?

Whenever the poor have cried, Caesar has wept;

Ambition should be made of sterner stuff.

But Brutus says he was ambitious;”.
using rhetorical questions does make you think about the logic of his argument

In this quote, Brutus is using pathos and by  saying that he loves caesar just as much as everyone else and trying to make himself sound appealing. He is also trying to get empathy from his audience, the Romans.