Final answer:
Cicero feared public backlash if he killed Catiline, as it could be seen as an overstep of authority or a breach of Roman legal norms.
Step-by-step explanation:
According to Cicero, as expressed in his writings against Catiline, if he were to kill Catiline, the expectation was that the public would offer harsh criticism and accusation. While not explicitly stated in the excerpts provided, the general context of his speeches and the political environment of the time suggest that Cicero feared being frowned upon for taking such drastic actions, as the public might view it as an overstep of his authority or a breaching of Roman legal norms. Instead, Cicero believed it was important to let the law and traditional processes resolve matters of treason and conspiracy that Catiline was accused of.