As Shakespeare characterizes Brutus, I would argue that Octavius in incorrect in his view of Brutus. While Brutus certainly believes in the power of words--so much so that he thinks he will be able to use oratory to convince Caesar's funeral crowd that he acted morally in assassinating Caesar--Brutus is also a man of action. After all, he physically participates in the assassination; he does not simply plan it. He goes to battle with Cassius against Antony and Octavius. And most significantly, he does not try to talk his way out of his fate at the play's end; rather, he commits suicide (again, he acts) because he believes that it is the noble action to take.
Octavius's statement reveals more about himself than it does about Brutus. While Antony fights tirelessly against Brutus and Cassius, Octavius spends much of his time plotting and talking rather than actually participating (at least for Shakespeare's characterization of him in Julius Caesar).