How is Cassius able to sway characters away from their moral code?

Cassius is able to convince Brutus that his close friend, Julius Caesar, is a threat to the Roman Republic and persuades Brutus to join the conspirators. Cassius is aware of Brutus's honorable nature and forms a brilliant argument that depicts Caesar as an enemy of Rome. Cassius tells Brutus that Caesar already believes that he is more exalted, accomplished, and better than any citizen or senator and plans to rule Rome as a monarch. Cassius also cites Caesar's ambitious nature to sway Brutus into joining the conspirators. In addition to presenting a moving argument that Caesar will destroy the Roman Republic for personal gain, Cassius also has false letters written by "concerned" citizens strategically placed where Brutus will find them. Cassius then appeals to Brutus's sense of duty by mentioning his revered ancestors, who defeated Rome's last emperor to establish the Republic. In summary, Cassius appeals to Brutus's honorable nature, gives numerous examples of Caesar's arrogance, plants false letters in his home, and argues that Caesar is an enemy of the Roman populace to convince Brutus to join the conspirators and assassinate Julius Caesar.