How did Brutus manipulate the conspirators in Act II Scene 1 of Julius Caesar?

Brutus’s tragic flaw is his idealism, and his blindness to the potential for evil in man.  He himself is honorable, and strives to justify his actions against Caesar in an honorable manner.  Likewise he paints the conspirators as well as murdering for honorable reasons, though this is not necessarily reality.  Given these propensities of our hero, we can see that as he is speaking to his fellow conspirators in Act II, Scene 1, one could argue that he isn’t so much manipulating others as he is manipulating himself, and persuading his allies to conform to his idea of an honorable murder for the betterment of Roman society.

When Cassius suggests that they take an oath of secrecy, Brutus dissents, and calls upon this honor as rendering any oath superfluous.  He protests,

…do not stain
The even virtue of our enterprise,
Nor th’insuppressive mettle of our spirits,
To think that or our cause or our performance
Did need an oath;

Thus he persuades the conspirators to forego any secret oaths to each other or to their cause, since the cause and the men themselves are noble, and such a virtuous act, among virtuous men, does itself solidify each man’s dedication to the plan.  And so Brutus compliments the others, and challenges their own moral fiber not only as honorable citizens, but also as Romans; the necessity of an oath is only for lesser men than they, for citizens of lesser civilizations.  This challenge forces the others to accept his suggestion, for fear of compromising their own reputations.

Brutus uses a similar tactic in lines 162 to 183 to dissuade the conspirators from assassinating Mark Antony.  “Let’s be sacrificers, but not butchers,” he implores to Cassius, “for Antony is but a limb of Caesar.”  He believes that Antony is harmless without Caesar’s leadership and support, and would have Caesar’s death be clean and honorable.  He will not have them contribute to a limb-hacking bloodbath, and calls upon the men’s reverence of the divine, asking them to “carve him as a dish fit for the gods,” and behave in a manner that will “make our purpose necessary, and not envious; …we shall be called purgers, not muderers.”  In this manner he seeks to persuade the conspirators to temperance in their deed, and therefore he, Brutus, will maintain his reputation for honesty and he can continue to live in his bubble of idealism and honor.  Which, of course, turns out after the fact to be impossible.